Friday, December 16, 2005
Bibliography on Quantum Programming Languages
This looks like a useful resource: Simon Gay's Bibliography on Quantum Programming Languages. It's surprisingly long. It's associated with a survey paper he wrote.
Saturday, December 10, 2005
Progress With Photons, and Jitter and Skew
[This posting serves as both the fourth installment in our series on scalability, and as the papers-of-the-week entry.]
Nature this week has three intriguing papers on progress in quantum information processing with photons. I'm at home, without access to our institutional Nature subscription, so all I can read is the first paragraph. Grumble.
Jeff Kimble's group at Caltech reports on Measurement-induced entanglement for excitation stored in remote atomic ensembles. Use 10^5 atoms at each of two sites, and quantum interference when one of them emits a photon creates a single entangled state. Hmm. "One joint excitation" is the phrase they use, but I'm a little fuzzy on why they're not creating a Bell state. I'm looking forward to reading the full paper.
The other two papers, from Kuzmich's group at Georgia Tech and Lukin's at Harvard, are on the use of atomic ensembles to store qubits that can be inserted and retrieved as single photons. These have the possibility to serve as memories, or at least as latches, for photons, providing an important tool for addressing problems I think are under-appreciated: jitter and skew. Without the ability to regenerate the timing of signals propagating through a large circuit, you can't claim to have scalability.
Clock handling is one of the most complex problems in classical chip design. Signal propagation across a chip requires significant amounts of time. It's subject to two significant error processes: jitter, in which the timing of a single signal varies from moment to moment as a result of noise, voltage fluctuations, etc., and skew, where different members of a group of signals arrive at different times because their path lengths vary. (Both of these problems are substantially worse in e.g., your SCSI cables.) We can also talk about "clock skew" as being a problem between regions of a chip.
In a quantum computer, as in a classical one, there are going to be times when we want things to be in sync. We may need pair of photons to arrive at the same place at the same time, for example. Electromagnetically induced transparency (EIT), sometimes called "stopped light", is an excellent candidate for helping here. A strong control beam (our latch clock) is focused on an atomic ensemble. Whether the beam is on or off can determine whether a separate photon (the data signal) is allowed to pass through the material, or is held in place. Thus, it can be used to align multiple photons, releasing them all to move out of the ensemble(s) at the same time. Up until now, EIT experiments have been done on classical waves; these are, as I understand it, the first reports of doing similar things for a single photon.
Prof. Harris at Stanford is one of the leading lights (sorry) in EIT. The Lukin group is another, and Prof. Kozuma of Tokyo Institute of Technology has some promising-looking work.
Nature this week has three intriguing papers on progress in quantum information processing with photons. I'm at home, without access to our institutional Nature subscription, so all I can read is the first paragraph. Grumble.
Jeff Kimble's group at Caltech reports on Measurement-induced entanglement for excitation stored in remote atomic ensembles. Use 10^5 atoms at each of two sites, and quantum interference when one of them emits a photon creates a single entangled state. Hmm. "One joint excitation" is the phrase they use, but I'm a little fuzzy on why they're not creating a Bell state. I'm looking forward to reading the full paper.
The other two papers, from Kuzmich's group at Georgia Tech and Lukin's at Harvard, are on the use of atomic ensembles to store qubits that can be inserted and retrieved as single photons. These have the possibility to serve as memories, or at least as latches, for photons, providing an important tool for addressing problems I think are under-appreciated: jitter and skew. Without the ability to regenerate the timing of signals propagating through a large circuit, you can't claim to have scalability.
Clock handling is one of the most complex problems in classical chip design. Signal propagation across a chip requires significant amounts of time. It's subject to two significant error processes: jitter, in which the timing of a single signal varies from moment to moment as a result of noise, voltage fluctuations, etc., and skew, where different members of a group of signals arrive at different times because their path lengths vary. (Both of these problems are substantially worse in e.g., your SCSI cables.) We can also talk about "clock skew" as being a problem between regions of a chip.
In a quantum computer, as in a classical one, there are going to be times when we want things to be in sync. We may need pair of photons to arrive at the same place at the same time, for example. Electromagnetically induced transparency (EIT), sometimes called "stopped light", is an excellent candidate for helping here. A strong control beam (our latch clock) is focused on an atomic ensemble. Whether the beam is on or off can determine whether a separate photon (the data signal) is allowed to pass through the material, or is held in place. Thus, it can be used to align multiple photons, releasing them all to move out of the ensemble(s) at the same time. Up until now, EIT experiments have been done on classical waves; these are, as I understand it, the first reports of doing similar things for a single photon.
Prof. Harris at Stanford is one of the leading lights (sorry) in EIT. The Lukin group is another, and Prof. Kozuma of Tokyo Institute of Technology has some promising-looking work.
Visiting L.A.: WCQIS, USC/ISI, and USC
Next week I'll be in L.A. Tuesday I'm giving a talk on "The Design of a Quantum Multicomputer" at ISI, Wednesday I'll be visiting USC, then Thurday-Sunday I'm at the Caltech Workshop on Classical & Quantum Information Security. I might be giving a short talk at WCQIS, but I'm not sure yet.
If you see me, stop me and say hi. I'm especially looking to meet people who are interested in quantum computer architecture.
If you see me, stop me and say hi. I'm especially looking to meet people who are interested in quantum computer architecture.
Thursday, December 08, 2005
Hayabusa: Good News and Bad News
Good news: JAXA is now saying that on Monday they recovered control of Hayabusa (the spacecraft that landed on an asteroid), and can probably bring it back to Earth as originally planned.
Bad news: the widget that was supposed to fire balls at the surface so they could collect the rebounding material apparently failed to fire.
? news: they think that just the landing might have kicked up some material into the collector, that they might be able to retrieve once the probe has returned to Earth.
Bad news: the widget that was supposed to fire balls at the surface so they could collect the rebounding material apparently failed to fire.
? news: they think that just the landing might have kicked up some material into the collector, that they might be able to retrieve once the probe has returned to Earth.
Saturday, December 03, 2005
3D Mid-Air Plasma Display
Remember the animated, holographic chess set in the first Star Wars?
Yesterday Keio had its annual Techno-Mall, a mini-exhibition where about sixty professors' labs set up booths and demonstrations to show off their research for the public, some alumni, the Keio brass, and funding bigwigs.
I was there with my physics professor Kohei Itoh's group, discussing our research on the silicon NMR quantum computer. My CS prof, Fumio Teraoka, had a nice demo of fast handovers in mobile IPv6. There was heavy emphasis on sustainable, environmentally friendly engineering, including a lecture by Kengo Kuma, a famous architect who is a visiting professor at Keio. A lot of research is also taking place on assistive technologies for the elderly and disabled. The bicycle that balances itself while you pedal, and the wheelchair that can help you lift your arm both look promising. Material science and computer science in various forms also seem to be strengths of Keio.
But the most startling thing I saw, by far, was a videotape. Prof.
Taro Uchiyama and his group have developed a display that can create glowing, animated images in mid-air, floating above the device itself. So far, they can do things like a fluttering butterfly, or three characters of text, totaling a hundred pixels or so. In a year, they hope to be animating fully 3D characters of the quality of, say, a human being built out of Legos.
What's the trick? They focus a laser down to a point small enough to create, for a moment, a glowing plasma in mid-air! They can scan the focus point in three dimensions, not really fast enough yet, but tolerable. In fact, it's a bit reminiscent of laserium light shows in its current incarnation, though it's white light only.
The images are currently table-top size, but Prof. Uchiyama thinks they can scale this up a long ways, and one of their posters shows a graphic of it being used by a lighthouse at the beach, skywriting tsunami warnings. How much power does this take? I asked, and got a non-answer, but that's presumably the reason they were demoing a videotape instead of the device. Students are in the demo, wearing very heavy safety goggles.
This is mind-bending stuff; I wonder how far they'll really be able to take it. I hope they succeed, both technically and commercially.
Unfortunately, I can't find anything about this on the web. Prof. Uchiyama says he's looking for someone to commercialize it, either here or in the U.S.
Yesterday Keio had its annual Techno-Mall, a mini-exhibition where about sixty professors' labs set up booths and demonstrations to show off their research for the public, some alumni, the Keio brass, and funding bigwigs.
I was there with my physics professor Kohei Itoh's group, discussing our research on the silicon NMR quantum computer. My CS prof, Fumio Teraoka, had a nice demo of fast handovers in mobile IPv6. There was heavy emphasis on sustainable, environmentally friendly engineering, including a lecture by Kengo Kuma, a famous architect who is a visiting professor at Keio. A lot of research is also taking place on assistive technologies for the elderly and disabled. The bicycle that balances itself while you pedal, and the wheelchair that can help you lift your arm both look promising. Material science and computer science in various forms also seem to be strengths of Keio.
But the most startling thing I saw, by far, was a videotape. Prof.
Taro Uchiyama and his group have developed a display that can create glowing, animated images in mid-air, floating above the device itself. So far, they can do things like a fluttering butterfly, or three characters of text, totaling a hundred pixels or so. In a year, they hope to be animating fully 3D characters of the quality of, say, a human being built out of Legos.
What's the trick? They focus a laser down to a point small enough to create, for a moment, a glowing plasma in mid-air! They can scan the focus point in three dimensions, not really fast enough yet, but tolerable. In fact, it's a bit reminiscent of laserium light shows in its current incarnation, though it's white light only.
The images are currently table-top size, but Prof. Uchiyama thinks they can scale this up a long ways, and one of their posters shows a graphic of it being used by a lighthouse at the beach, skywriting tsunami warnings. How much power does this take? I asked, and got a non-answer, but that's presumably the reason they were demoing a videotape instead of the device. Students are in the demo, wearing very heavy safety goggles.
This is mind-bending stuff; I wonder how far they'll really be able to take it. I hope they succeed, both technically and commercially.
Unfortunately, I can't find anything about this on the web. Prof. Uchiyama says he's looking for someone to commercialize it, either here or in the U.S.
Friday, December 02, 2005
6.4 Off the Coast of Miyagi-ken
As long as I'm keeping track of recent quakes, we had a 6.4 a couple of hundred kilometers north of here at 22:13 local time. There was only a little shaking here, but I was in the bathtub (oops, is that too much information?), which was an interesting experience. Not strong enough to feel quite like the agitate cycle...No reports of any damage; it only reach 3 on the Japanese subjective shaking scale.
Coming up after I can get it typed in, a report on Keio's 3D mid-air animated plasma display...
Coming up after I can get it typed in, a report on Keio's 3D mid-air animated plasma display...
Thursday, December 01, 2005
Fireball Over Abiko?
At 22:18 Japan time, as I was walking home, I saw something I can't quite explain. A bright light came over a house that was blocking my view to the west, split in two, then forked a third. The first two were bluish-white, the third orange. It looked like a Roman candle, but didn't show any ballistic arc, just the path of a meteor. It petered out overhead, near Mars, having covered about 30 degrees of sky. It was brighter than Mars, but not impossibly bright, comparable to or slightly brighter than the brightest meteors I've seen.
This is in Abiko, northeast of Tokyo, at roughly 35.88N 140.03E.
This is in Abiko, northeast of Tokyo, at roughly 35.88N 140.03E.
Reading Out Multiple Ions Simultaneously
I'm catching up a little on my reading, so expect a fair number of paper reviews over the next week or so. Most of these will be quantum computing papers with a focus on how large systems are going to develop.
Starting from the top of the stack, Mark Acton and company from Chris Monroe's lab at Michigan just posted the paper Near-Perfect Simultaneous Measurement of a Qubit Register on the arXiv. This is one of a string of excellent papers to come out of Monroe's lab in the last half year or so.
Acton et al. are measuring ions in an ion trap using an intensified CCD. They use the hyperfine states of 111Cd+ ions in a linear trap as the qubits. A photocathode and fluorescent screen are used to intensify the photons coming from the ions themselves, then focused onto a small CCD. In their example, a 4x4 group of pixels is grouped into a single pixel, and a 7x7 block of those is used to detect each ion. Readout time is 15msec for the whole CCD right now; they claim reducing that to 2.5usec/ion is doable with currently available CCDs. One limit in their current setup is the waist of the detection beam is about 10 microns, compared to an ion spacing of 4um. They achieved readout accuracy of 98%, and a significant part of the inaccuracy is believed to be due to neighboring ions influencing each other. Done on a chain of three ions, the paper includes images of binary counting from 000 to 111.
This paper is important because concurrent readout of ions is critical for making quantum error correction work, as well as generally running algorithms faster. Rather than reading the ions in-place in a single trap, of course, the ions could be moved apart first, but that movement can create errors, and of course if they are separated then you have to have multiple laser beams for the detection. Beyond the beam waist problem, it's not clear to me what limits the number of ions this can scale to, but in general we are interested in only a few per trap at a time, so it should work.
When I visited Andrew Steane at Oxford in January, he had an old printout on his door showing pictures of binary states up to some larger number; 63 or maybe even 127? At first glance, this appears to be similar to that work, though I don't know much about the Steane experiments. I suspect those were more about the preparation of the numeric states, whereas this is about how to build a detector that can work reliably for multiple ions. At any rate, the accuracy of Acton's detection is remarkably good, and bodes well for continuing work on ion traps.
[Update, 12/2: the pontiff has a posting on a couple of other recent, good ion trap papers.]
Starting from the top of the stack, Mark Acton and company from Chris Monroe's lab at Michigan just posted the paper Near-Perfect Simultaneous Measurement of a Qubit Register on the arXiv. This is one of a string of excellent papers to come out of Monroe's lab in the last half year or so.
Acton et al. are measuring ions in an ion trap using an intensified CCD. They use the hyperfine states of 111Cd+ ions in a linear trap as the qubits. A photocathode and fluorescent screen are used to intensify the photons coming from the ions themselves, then focused onto a small CCD. In their example, a 4x4 group of pixels is grouped into a single pixel, and a 7x7 block of those is used to detect each ion. Readout time is 15msec for the whole CCD right now; they claim reducing that to 2.5usec/ion is doable with currently available CCDs. One limit in their current setup is the waist of the detection beam is about 10 microns, compared to an ion spacing of 4um. They achieved readout accuracy of 98%, and a significant part of the inaccuracy is believed to be due to neighboring ions influencing each other. Done on a chain of three ions, the paper includes images of binary counting from 000 to 111.
This paper is important because concurrent readout of ions is critical for making quantum error correction work, as well as generally running algorithms faster. Rather than reading the ions in-place in a single trap, of course, the ions could be moved apart first, but that movement can create errors, and of course if they are separated then you have to have multiple laser beams for the detection. Beyond the beam waist problem, it's not clear to me what limits the number of ions this can scale to, but in general we are interested in only a few per trap at a time, so it should work.
When I visited Andrew Steane at Oxford in January, he had an old printout on his door showing pictures of binary states up to some larger number; 63 or maybe even 127? At first glance, this appears to be similar to that work, though I don't know much about the Steane experiments. I suspect those were more about the preparation of the numeric states, whereas this is about how to build a detector that can work reliably for multiple ions. At any rate, the accuracy of Acton's detection is remarkably good, and bodes well for continuing work on ion traps.
[Update, 12/2: the pontiff has a posting on a couple of other recent, good ion trap papers.]
Hayabusa in Trouble?
A few days ago, I reported happily about Hayabusa's visit to an asteroid. Today, there is less happy news; the probe is having engine trouble, apparently is unable to control its attitude, and may not be able to return to Earth as planned. Apparently, there's a good chance that it could come back anyway, four or five years late; they will have to make a decision about whether to continue funding for the project, or cut their losses. (The Hayabusa project home page seems to be several days out of date, in both Japanese and English; how can that be acceptable?)
The Daily Yomiuri article about the problems is extremely critical of JAXA, the Japan Aerospace Exploration Agency. JAXA was just created a couple of years ago by merging two separate agencies, and reportedly factionalism still exists inside the organization. The article ends with rather dour warnings that JAXA needs to do a better job of explaining itself and its research to the public, as well as fix its technical problems.
On a different topic, the article also makes mention of JAXA's successful test of a model for a supersonic jetliner, done in Australia in October. I somehow missed this, but there's a good article at the Register (including links to the flight data at JAXA) and video of the launch at the BBC (in both Windows Media and Real formats, though I swear it looks like somebody videotaped a TV, rather than used an actual feed). The goal is reportedly a 300-seat Mach 2 airliner that's as fuel- and noise-friendly as a current jumbo jet (which is to say, not very, but a heck of a lot better than the Concorde). Unfortunately, they are speculating that it won't fly until 2020 or 2025.
The Daily Yomiuri article about the problems is extremely critical of JAXA, the Japan Aerospace Exploration Agency. JAXA was just created a couple of years ago by merging two separate agencies, and reportedly factionalism still exists inside the organization. The article ends with rather dour warnings that JAXA needs to do a better job of explaining itself and its research to the public, as well as fix its technical problems.
On a different topic, the article also makes mention of JAXA's successful test of a model for a supersonic jetliner, done in Australia in October. I somehow missed this, but there's a good article at the Register (including links to the flight data at JAXA) and video of the launch at the BBC (in both Windows Media and Real formats, though I swear it looks like somebody videotaped a TV, rather than used an actual feed). The goal is reportedly a 300-seat Mach 2 airliner that's as fuel- and noise-friendly as a current jumbo jet (which is to say, not very, but a heck of a lot better than the Concorde). Unfortunately, they are speculating that it won't fly until 2020 or 2025.
International Robot Exhibition
This is mostly a heads up for those of you around Tokyo -- the 2005 International Robot Exhibition is taking place yesterday through Saturday (Dec. 3). Some of the same robots that were at the Aichi Expo are there, but this is primarily an industry trade show, not a tourist attraction or educational exhibit. Nevertheless, I'm going to try to go on Saturday; if I manage to, I'll definitely report back, hopefully with photos.
Monday, November 28, 2005
Mom, Your Teapot Emailed Me, And...
The Daily Yomiuri reports today on some new inventions intended to invade your privacy, er, help the kids of the elderly make sure they are okay. (The article is bylined "The Yomiuri Shimbun", which I often suspect means they are cribbing from press releases.)
The first one is an electric hot water maker for tea (a "potto", or hot pot) from Zojirushi (the biggest hot pot maker). The i-Pot is the first product in their "Mimamori" ("keeping an eye out") service. (Website is here, but Japanese only; a few photos are here.) It has a built-in DoCoMo DoPa packet radio transceiver, and sends email twice a day to a designated list of recipients with the recent usage records, or you can poll it to find out the latest. The pot is 5,250 yen (about $50), then the service is 3,150 ($30) a month. They claim to have more than 2,500 customers already.
I've never seen my mother-in-law drink water; she drinks tea continuously. But what if yours doesn't? Not to worry, ArtData can attach sensors to everything from your refrigerator door to the toilet floor mat to check up on you. Paramount Bed Co. makes an adjustable (hospital-style) bed that will report the height and tilt of the bed via some sort of wireless, and Yozan has a gadget based on a two-way pager that the city government of Wako, Saitama Prefecture is deploying. A local government official sends you a message each morning, and you respond by pressing one of the three buttons, "well", "not well", or "call me".
The privacy implications are not going unnoticed, but Japan is most decidedly coming down on the side of more information. Helping the community take better care of the rapidly aging population here is seen as the principal imperative.
The first one is an electric hot water maker for tea (a "potto", or hot pot) from Zojirushi (the biggest hot pot maker). The i-Pot is the first product in their "Mimamori" ("keeping an eye out") service. (Website is here, but Japanese only; a few photos are here.) It has a built-in DoCoMo DoPa packet radio transceiver, and sends email twice a day to a designated list of recipients with the recent usage records, or you can poll it to find out the latest. The pot is 5,250 yen (about $50), then the service is 3,150 ($30) a month. They claim to have more than 2,500 customers already.
I've never seen my mother-in-law drink water; she drinks tea continuously. But what if yours doesn't? Not to worry, ArtData can attach sensors to everything from your refrigerator door to the toilet floor mat to check up on you. Paramount Bed Co. makes an adjustable (hospital-style) bed that will report the height and tilt of the bed via some sort of wireless, and Yozan has a gadget based on a two-way pager that the city government of Wako, Saitama Prefecture is deploying. A local government official sends you a message each morning, and you respond by pressing one of the three buttons, "well", "not well", or "call me".
The privacy implications are not going unnoticed, but Japan is most decidedly coming down on the side of more information. Helping the community take better care of the rapidly aging population here is seen as the principal imperative.
Sunday, November 27, 2005
Stop Me If You've Heard This One Before...
Found via these four physics blogs, a Register article saying that Maxell will be offering holographic storage developed by InPhase Technologies by late 2006. 300GB, 20MB/sec. (what's the access time?), roadmap to 1.6TB/disk.
Creating a new, removable, random-access, high-performance storage medium is really hard. For optical things, the readers/writers tend to be expensive; to amortize that cost and get competitive GB/$, you want to make it removable, which means you have to lock in a data format for years, which hurts your density growth (while fixed magnetic disks are growing at 60-100%/year), makes more complex mechanics, makes it harder to keep the head on track, and makes serious demands on interoperability of readers and writers. The heavier optical heads make fast seek times problematic, too.
Good luck to them. I hope they have better luck than ASACA (where I'm proud to say I worked on just such a difficult project; I'm sad to say it failed, but the company still does well with autochangers for many media types), Terastor (whose website claims $100M in development generated 90 patents; too bad no successful drives/media came out), Quinta (now completely gone, as far as I can tell; absorbed back into Seagate?), Holoplex (gone), Tamarack (gone?), and a host of others did on high-speed magneto-optical, near-field magneto-optical, and holographic storage media.
I can only think of five successful removable, rotating media types: three sizes of floppy disk, CDs, and DVDs. You might throw in the first MO (600MB) and one or two types of removable hard disk, if you're generous. The newer optical media require long lead time, large corporate consortia, and enormous standards, marketing, and manufacturing efforts.
Will this finally be holographic storage's breakthrough? Stay tuned...
[Update: Sam Coleman, one of the gods of supercomputer mass storage and hierarchical mass storage, says he first saw holographic storage in 1979, and delivery was promised in eighteen months. Sam found this page with a little such history on it.]
Creating a new, removable, random-access, high-performance storage medium is really hard. For optical things, the readers/writers tend to be expensive; to amortize that cost and get competitive GB/$, you want to make it removable, which means you have to lock in a data format for years, which hurts your density growth (while fixed magnetic disks are growing at 60-100%/year), makes more complex mechanics, makes it harder to keep the head on track, and makes serious demands on interoperability of readers and writers. The heavier optical heads make fast seek times problematic, too.
Good luck to them. I hope they have better luck than ASACA (where I'm proud to say I worked on just such a difficult project; I'm sad to say it failed, but the company still does well with autochangers for many media types), Terastor (whose website claims $100M in development generated 90 patents; too bad no successful drives/media came out), Quinta (now completely gone, as far as I can tell; absorbed back into Seagate?), Holoplex (gone), Tamarack (gone?), and a host of others did on high-speed magneto-optical, near-field magneto-optical, and holographic storage media.
I can only think of five successful removable, rotating media types: three sizes of floppy disk, CDs, and DVDs. You might throw in the first MO (600MB) and one or two types of removable hard disk, if you're generous. The newer optical media require long lead time, large corporate consortia, and enormous standards, marketing, and manufacturing efforts.
Will this finally be holographic storage's breakthrough? Stay tuned...
[Update: Sam Coleman, one of the gods of supercomputer mass storage and hierarchical mass storage, says he first saw holographic storage in 1979, and delivery was promised in eighteen months. Sam found this page with a little such history on it.]
A Visit to an Asteroid
I don't know if this is making much news elsewhere, but the Japanese probe Hayabusa touched down on the asteroid Itokawa on Saturday, and is believed to have retrieved soil samples which it will hopefully return to Earth next June.
This is the first landing on a body other than the Moon, Mars, and Venus [note: that's what their press release said, but they've apparently forgotten about Cassini-Huygens' landing on Titan], and the first by a country other than the U.S. or U.S.S.R./Russia. If the sample return succeeds, it will be the first sample return (by anyone) from beyond the Moon's orbit, too. The probe uses an ion engine, which is very advanced technology, and had to navigate and land autonomously due to the distances involved, which is impressive. It hasn't all been smooth; this was the second landing/sample retrieval attempt, and a secondary probe failed to land, as well.
Itokawa is a fascinating asteroid; it has no craters. It looks a little like Joshua Tree, with lots of rocks sticking up out of a dusty plain.
A somewhat broken English news release is here, better pictures on the Japanese page here, current status (English) here, and the English project home page here.
This is the first landing on a body other than the Moon, Mars, and Venus [note: that's what their press release said, but they've apparently forgotten about Cassini-Huygens' landing on Titan], and the first by a country other than the U.S. or U.S.S.R./Russia. If the sample return succeeds, it will be the first sample return (by anyone) from beyond the Moon's orbit, too. The probe uses an ion engine, which is very advanced technology, and had to navigate and land autonomously due to the distances involved, which is impressive. It hasn't all been smooth; this was the second landing/sample retrieval attempt, and a secondary probe failed to land, as well.
Itokawa is a fascinating asteroid; it has no craters. It looks a little like Joshua Tree, with lots of rocks sticking up out of a dusty plain.
A somewhat broken English news release is here, better pictures on the Japanese page here, current status (English) here, and the English project home page here.
Saturday, November 26, 2005
Ion Trap Quantum Computer Architecture
With the deadline for the 2006 conference in a week, it seems like a good time to talk about the International Symposium on Computer Architecture. ISCA is the premiere forum for architecture research; it's very competitive and papers there are, as a rule, highly cited.
Mark Oskin's group published a good ion trap system architecture paper in ISCA 2005. The paper "An Evaluation Framework and Instruction Set Architecture for Ion-Trap based Quantum Micro-architectures" shows how to take the technology designed by the Wineland group at NIST and begin designing a complete computer out of it. They evaluate different choices of layout: how many traps per segment of wire, how to minimize the number of turns an ion must make, etc. They also discuss their tool chain for doing much of the work.
When we systems folk (there are only a handful of us in quantum computing, with Mark leading the class) talk about architecture, this is the kind of thing we mean. This work suggests that most of the decoherence in an ion trap system will come from turning corners, and therefore the research they are doing has the potential to have a dramatic effect on the practical threshold necessary for QEC to be effective.
[Disclaimer: Mark and I have a joint paper under consideration, though I had nothing to do with the work described here.]
Mark Oskin's group published a good ion trap system architecture paper in ISCA 2005. The paper "An Evaluation Framework and Instruction Set Architecture for Ion-Trap based Quantum Micro-architectures" shows how to take the technology designed by the Wineland group at NIST and begin designing a complete computer out of it. They evaluate different choices of layout: how many traps per segment of wire, how to minimize the number of turns an ion must make, etc. They also discuss their tool chain for doing much of the work.
When we systems folk (there are only a handful of us in quantum computing, with Mark leading the class) talk about architecture, this is the kind of thing we mean. This work suggests that most of the decoherence in an ion trap system will come from turning corners, and therefore the research they are doing has the potential to have a dramatic effect on the practical threshold necessary for QEC to be effective.
[Disclaimer: Mark and I have a joint paper under consideration, though I had nothing to do with the work described here.]
Friday, November 25, 2005
Music Review: Tatopani at Sweet Basil
Double disclaimer: number one, Robbie Belgrade is a friend of mine, number two, the music of Tatopani is exactly the kind of music I like :-). So, your mileage may vary.
Last night Mayumi and I snuck out to hear Tatopani play at Sweet Basil in Roppongi. They were playing a (sold out!) release party for their new CD, Azure (which has been reviewed by Daily Yomiuri, Mainichi, and Japan Times, so if you don't trust my review, try them).
I have heard Robbie play with a couple of other groups; I like this one the best, by far. Tatopani is Robbie, Chris Hardy, and Andy Bevan, with the new addition of Bruce Stark, all of whom have lived in Tokyo for a long time.
So what's the music? One of them described Tatopani as "kick-ass world music" in an interview. That's as good a description as any I could come up with; I don't have the technical vocabulary to explain it. If you like, say, Yo-Yo Ma's Silk Road albums, recent Wayne Shorter, and Dave Brubek's "Blue Rondo a la Turk", you're going to like Tatopani. This is not the "world pop" of somebody like Angelique Kidjo, nor the driving rock-influenced work of Joe Zawinul. The rhythms are complex, but there is a lot of space in the music, and indeed they name Miles Davis' "Bitches Brew" as an influence.
All of the guys play an array of instruments. Robbie's preferred woodwind axe is a bass clarinet, but I might actually like his sax playing better. For good measure, he plays a very mean tabla, and a pandeira (Brazilian tambourine) that has remarkable expressiveness. Chris's percussion setup looks like he went into a percussion store and bought one of everything. He had seven gongs, eleven cymbals, a djembe, another African drum (ashiko, maybe?), a wooden box, a doumbek with a high, crisp sound, and on and on. On one tune, he played a terracotta vase which had a nice bass and a higher, clear sustain. Andy played soprano sax, didjeridoo, flute, and some percussion. He played a kalimba (African alto music box played with your thumbs, more or less) on one very nice tune, "El Jinete". Bruce is the slacker in the instrument count department; he stuck with acoustic and electric pianos, except for one tune he contributed some percussion to.
Most of the tunes on Azure were written by Robbie. Some start with a spacious, slow opening before moving into more up-tempo sections. I really like the bass groove Bruce lays down on the opening track, "Azure". As you'd expect with a group like this, the rhythms are hideously complex in places; one tune is in 11/4 time (named, not coincidentally, "Eleven"), and I couldn't identify the time signatures on a couple. They opened their second set with "Bat Dance", by Chris, in which Robbie and Andy support a long, complex, exciting solo by Chris on the frame drum. The range of sounds ten fingers can get out of a piece of skin stretched across a wide, shallow wooden frame is simply amazing.
Sweet Basil is a great place to hear music. It's new, the food and sound are quite good, and the ventilation keeps the smoke level down. The desserts were excellent, and the potato soup rich. Mayumi had duck and I had lamb for main dishes; they needed a little salt and pepper, but were well prepared and presented. If you're headed there, make reservations, and show up early. Seating is by order of arrival. Tatopani sold out; I would guess the place probably holds 2-300 people. We got there early enough for good, but not great, seats, about 7:00.
The web site only lists last night's gig, but they were talking about a number of other appearances scheduled around Japan in the next several months. Hopefully they'll post a schedule soon. I know Chris is playing a percussion duo concert with, um, I'm having trouble reading the name, Shoko Aratani? at Philia Hall on March 4.
Hmm, Chris and Shoko are also playing with Eitetsu Hayashi on December 23rd? Hayashi is the taiko player of whom another professional musician said, "When Eitetsu plays, times stops and you can hear the Universe breathe." He's astonishing. See this if you can!
Tatopani's CDs can be ordered through their web site, where you'll also find sound samples.
Last night Mayumi and I snuck out to hear Tatopani play at Sweet Basil in Roppongi. They were playing a (sold out!) release party for their new CD, Azure (which has been reviewed by Daily Yomiuri, Mainichi, and Japan Times, so if you don't trust my review, try them).
I have heard Robbie play with a couple of other groups; I like this one the best, by far. Tatopani is Robbie, Chris Hardy, and Andy Bevan, with the new addition of Bruce Stark, all of whom have lived in Tokyo for a long time.
So what's the music? One of them described Tatopani as "kick-ass world music" in an interview. That's as good a description as any I could come up with; I don't have the technical vocabulary to explain it. If you like, say, Yo-Yo Ma's Silk Road albums, recent Wayne Shorter, and Dave Brubek's "Blue Rondo a la Turk", you're going to like Tatopani. This is not the "world pop" of somebody like Angelique Kidjo, nor the driving rock-influenced work of Joe Zawinul. The rhythms are complex, but there is a lot of space in the music, and indeed they name Miles Davis' "Bitches Brew" as an influence.
All of the guys play an array of instruments. Robbie's preferred woodwind axe is a bass clarinet, but I might actually like his sax playing better. For good measure, he plays a very mean tabla, and a pandeira (Brazilian tambourine) that has remarkable expressiveness. Chris's percussion setup looks like he went into a percussion store and bought one of everything. He had seven gongs, eleven cymbals, a djembe, another African drum (ashiko, maybe?), a wooden box, a doumbek with a high, crisp sound, and on and on. On one tune, he played a terracotta vase which had a nice bass and a higher, clear sustain. Andy played soprano sax, didjeridoo, flute, and some percussion. He played a kalimba (African alto music box played with your thumbs, more or less) on one very nice tune, "El Jinete". Bruce is the slacker in the instrument count department; he stuck with acoustic and electric pianos, except for one tune he contributed some percussion to.
Most of the tunes on Azure were written by Robbie. Some start with a spacious, slow opening before moving into more up-tempo sections. I really like the bass groove Bruce lays down on the opening track, "Azure". As you'd expect with a group like this, the rhythms are hideously complex in places; one tune is in 11/4 time (named, not coincidentally, "Eleven"), and I couldn't identify the time signatures on a couple. They opened their second set with "Bat Dance", by Chris, in which Robbie and Andy support a long, complex, exciting solo by Chris on the frame drum. The range of sounds ten fingers can get out of a piece of skin stretched across a wide, shallow wooden frame is simply amazing.
Sweet Basil is a great place to hear music. It's new, the food and sound are quite good, and the ventilation keeps the smoke level down. The desserts were excellent, and the potato soup rich. Mayumi had duck and I had lamb for main dishes; they needed a little salt and pepper, but were well prepared and presented. If you're headed there, make reservations, and show up early. Seating is by order of arrival. Tatopani sold out; I would guess the place probably holds 2-300 people. We got there early enough for good, but not great, seats, about 7:00.
The web site only lists last night's gig, but they were talking about a number of other appearances scheduled around Japan in the next several months. Hopefully they'll post a schedule soon. I know Chris is playing a percussion duo concert with, um, I'm having trouble reading the name, Shoko Aratani? at Philia Hall on March 4.
Hmm, Chris and Shoko are also playing with Eitetsu Hayashi on December 23rd? Hayashi is the taiko player of whom another professional musician said, "When Eitetsu plays, times stops and you can hear the Universe breathe." He's astonishing. See this if you can!
Tatopani's CDs can be ordered through their web site, where you'll also find sound samples.
Wednesday, November 23, 2005
Japanese Gov't to Reward Cybersecurity
The Daily Yomiuri reports today that a tax credit enacted in 2003 will expire at the end of the fiscal year, as originally planned. 10 percent of the purchase price of "IT devices" (from PCs to fax machines; not including software?) is deducted directly directly from corporate tax. In fiscal 2005, companies will save about 510 billion yen (almost five billion U.S. dollars). (I have lots of questions about the aims and success of this measure, especially regarding software, but that's not the point of this posting.)
In its place, the government is considering enacting a package to improve the international competitiveness of companies. One provision may be a similar deduction of "10 percent of the retail price of database management software and other devices aimed at preventing illegal computer access, the use of spyware and information leak among other incidents."
That's a noble but vague goal; I could argue that practically anything was bought to further my cybersecurity. Moreover, security is more about practices than purchases.
I also wonder if companies that create cybersecurity problems a la Sony will have their taxes raised?
In its place, the government is considering enacting a package to improve the international competitiveness of companies. One provision may be a similar deduction of "10 percent of the retail price of database management software and other devices aimed at preventing illegal computer access, the use of spyware and information leak among other incidents."
That's a noble but vague goal; I could argue that practically anything was bought to further my cybersecurity. Moreover, security is more about practices than purchases.
I also wonder if companies that create cybersecurity problems a la Sony will have their taxes raised?
Tuesday, November 22, 2005
Shinkansen in China
The Yoimuri Shimbun is reporting today that China will buy sixty Hayate shinkansen (bullet trains) from a consortium of Japanese companies for its planned 12,000km network of high-speed trains. Apparently they will also buy ICE trains from Germany, but not TGV trains from France. No idea how they plan to apportion the different technologies; by region?
Hayate trains currently run at up to 275kph, though JR East is said to be working on speeds up to 360. The Chinese network is proposed to run at 300.
The report says the network will cost more than ten trillion yen (about 80 billion dollars), but doesn't say how many years it will take to do the whole buildout (though some services may start as early as 2008), nor what fraction of that money will be spent on Japanese-made rolling stock. Nikkei says the Hayate trains cost 250 million yen ($2M) per car, and I think those trains are typically ten cars, times sixty trains, that's $1.2 billion dollars.
And in America we have only the Acela, and only in a small area.
Hayate trains currently run at up to 275kph, though JR East is said to be working on speeds up to 360. The Chinese network is proposed to run at 300.
The report says the network will cost more than ten trillion yen (about 80 billion dollars), but doesn't say how many years it will take to do the whole buildout (though some services may start as early as 2008), nor what fraction of that money will be spent on Japanese-made rolling stock. Nikkei says the Hayate trains cost 250 million yen ($2M) per car, and I think those trains are typically ten cars, times sixty trains, that's $1.2 billion dollars.
And in America we have only the Acela, and only in a small area.
How Many Qubits Can Dance on the Head of a Pin?
[Third installment in examining the meaning of scaling a quantum computer. First is here, second one is here. Continued in installment four, here]
I have the cart slightly before the horse in my breadbox posting. In that posting, we were talking about a multi-node quantum computer and its relationship to scalability. But before getting to my quantum multicomputer, we should look at the scalability of a single, large, monolithic machine.
Again, let's consider VLSI-based qubits. In particular, let's look at the superconducting Josephson-junction flux qubit from Dr. Semba's group at NTT (one good paper on it is this one). Their qubit is a loop about 10 microns square. This area is determined by physics, not limited by VLSI feature size; the size of the loop determines the size of the flux quantum, which in turn determines control frequencies, gate speed, and whatnot. (The phase qubit from NIST is more like 100 microns on a side; it's big enough to see!) Semba-san's group is working hard on connecting qubits via an LC oscillator. The paper cited above shows that one qubit couples to the bus; the next step might be two qubits.
So, once they've achieved that, is it good enough? Do they then meet DiVincenzo's criterion for a scalable set of qubits? Let's see. As an engineer, I don't care if the technology scales indefinitely, I care if it scales through regions that solve interesting problems. In this case, we're looking for up to a quarter of a million physical qubits. Can we fit them on a chip? At first glance, it would seem so. Even a small 10mm square chip would fit a million 10-micron square structures. But that ignores I/O pads. Equally important, a glance at the micrograph in the paper above shows that the capacitor is huge compared to the qubit (but you only need one of those per bus that connects a modest-sized group of qubits, and it may be possible to build the capacitor in some more space-efficient manner, or maybe even put it off-chip?). Still more important, these qubits are magnetic, not charge; place them too close together, and they'll interfere. I have no idea what the spacing is (though I assume Semba-san and the others working on this type of qubit have at least thought about this, and may even have published some numbers in a paper I haven't read or don't recall). Control is achieved with a microwave line run past the qubit, so obviously you can't run that too close to other qubits. All of this is a long-winded way of saying there's a lot of physics to be done even before the mundane engineering of floor-planning. We talked a little in the last installment about the need for I/O pads and control lines into/out of the dil fridge. That applies directly to the chip, as well; now we need roughly a pin per qubit, unless a lot more of the signal generators and whatnot can be built directly into our device. Without some pretty major advances in integration, I'll be surprised if you can get more than a thousand qubits into a chip (whether they're charge, spin, flux, what have you). So does that mean we're dead? We can't reach a quarter of a million qubits?
The basic idea of the quantum multicomputer is that we can connect multiple nodes together. We need to create an entangled state that crosses node boundaries, so we need quantum I/O. So, you need the ability to entangle your stationary qubit with something that moves - preferably a photon, though an electron isn't out of the question; a strong laser probe beam may work, too. Then you need a way to get the information out of that photon back into another qubit at the destination node. This is going to be hard, but the alternative is a quantum computer that doesn't extend outside the confines of a single chip. This idea of distributed quantum computing goes back a decade, and there have been some good experiments in this area; I'll post some links references another time.
Bottom line: for the foreseeable future, scalability requires I/O - classical for sure, and maybe quantum. More than a matter of die space for the qubits themselves, I/O pads and lines and space for them on-chip, plus physical interference effects, will drive how many qubits you can fit on a chip. If that number doesn't scale up to the point where it is not the limiting factor in the size of system you can build, then you have to have quantum I/O (some way to entangle on-chip qubits with qubits in another device or another technology).
[Update: Semba-san tells me that the strength of the interaction could be a problem if the qubits are only a micron apart, but at 10um spacing, the interaction drops to order of kHz, low enough not to worry about much.]
I have the cart slightly before the horse in my breadbox posting. In that posting, we were talking about a multi-node quantum computer and its relationship to scalability. But before getting to my quantum multicomputer, we should look at the scalability of a single, large, monolithic machine.
Again, let's consider VLSI-based qubits. In particular, let's look at the superconducting Josephson-junction flux qubit from Dr. Semba's group at NTT (one good paper on it is this one). Their qubit is a loop about 10 microns square. This area is determined by physics, not limited by VLSI feature size; the size of the loop determines the size of the flux quantum, which in turn determines control frequencies, gate speed, and whatnot. (The phase qubit from NIST is more like 100 microns on a side; it's big enough to see!) Semba-san's group is working hard on connecting qubits via an LC oscillator. The paper cited above shows that one qubit couples to the bus; the next step might be two qubits.
So, once they've achieved that, is it good enough? Do they then meet DiVincenzo's criterion for a scalable set of qubits? Let's see. As an engineer, I don't care if the technology scales indefinitely, I care if it scales through regions that solve interesting problems. In this case, we're looking for up to a quarter of a million physical qubits. Can we fit them on a chip? At first glance, it would seem so. Even a small 10mm square chip would fit a million 10-micron square structures. But that ignores I/O pads. Equally important, a glance at the micrograph in the paper above shows that the capacitor is huge compared to the qubit (but you only need one of those per bus that connects a modest-sized group of qubits, and it may be possible to build the capacitor in some more space-efficient manner, or maybe even put it off-chip?). Still more important, these qubits are magnetic, not charge; place them too close together, and they'll interfere. I have no idea what the spacing is (though I assume Semba-san and the others working on this type of qubit have at least thought about this, and may even have published some numbers in a paper I haven't read or don't recall). Control is achieved with a microwave line run past the qubit, so obviously you can't run that too close to other qubits. All of this is a long-winded way of saying there's a lot of physics to be done even before the mundane engineering of floor-planning. We talked a little in the last installment about the need for I/O pads and control lines into/out of the dil fridge. That applies directly to the chip, as well; now we need roughly a pin per qubit, unless a lot more of the signal generators and whatnot can be built directly into our device. Without some pretty major advances in integration, I'll be surprised if you can get more than a thousand qubits into a chip (whether they're charge, spin, flux, what have you). So does that mean we're dead? We can't reach a quarter of a million qubits?
The basic idea of the quantum multicomputer is that we can connect multiple nodes together. We need to create an entangled state that crosses node boundaries, so we need quantum I/O. So, you need the ability to entangle your stationary qubit with something that moves - preferably a photon, though an electron isn't out of the question; a strong laser probe beam may work, too. Then you need a way to get the information out of that photon back into another qubit at the destination node. This is going to be hard, but the alternative is a quantum computer that doesn't extend outside the confines of a single chip. This idea of distributed quantum computing goes back a decade, and there have been some good experiments in this area; I'll post some links references another time.
Bottom line: for the foreseeable future, scalability requires I/O - classical for sure, and maybe quantum. More than a matter of die space for the qubits themselves, I/O pads and lines and space for them on-chip, plus physical interference effects, will drive how many qubits you can fit on a chip. If that number doesn't scale up to the point where it is not the limiting factor in the size of system you can build, then you have to have quantum I/O (some way to entangle on-chip qubits with qubits in another device or another technology).
[Update: Semba-san tells me that the strength of the interaction could be a problem if the qubits are only a micron apart, but at 10um spacing, the interaction drops to order of kHz, low enough not to worry about much.]
Sunday, November 20, 2005
Joint Chip Plant in Japan in 2007?
The Yomiuri Shimbun is reporting that five Japanese semiconductor makers, Hitachi, Toshiba, Matsushita Electric Industrial, NEC Electronics, and Renesas Technology, are planning a 65-nanometer wire width plant. It will be the first time Japanese manufacturers have done a joint chip plant.
Construction is expected to start next year, production in 2007 "at the earliest". Cost might be 200 billion yen (almost two billion U.S. dollars); the share to be paid by each company hasn't been determined yet. The article says it's necessary to keep the companies competitive in the face of "huge capital investments" by South Korean and U.S. manufacturers. I don't think they've picked a location yet.
Construction is expected to start next year, production in 2007 "at the earliest". Cost might be 200 billion yen (almost two billion U.S. dollars); the share to be paid by each company hasn't been determined yet. The article says it's necessary to keep the companies competitive in the face of "huge capital investments" by South Korean and U.S. manufacturers. I don't think they've picked a location yet.
Blogalog: Computer Graphics in Japan?
A pure computer graphics question, the first in a while. I know SIGGRAPH was months ago, but I never got around to asking some of my questions.
Was there any CG art (still or animated) from Japan this year? Who, from what organization? (Got a link?)
Any good technical papers from Japan, or exciting new technology from Japan on the show floor?
I know there are a lot of CG artists in Japan, and I'm not in that circle. It would be fun to get hooked up with them and at least attend the occasional talk or art show.
Was there any CG art (still or animated) from Japan this year? Who, from what organization? (Got a link?)
Any good technical papers from Japan, or exciting new technology from Japan on the show floor?
I know there are a lot of CG artists in Japan, and I'm not in that circle. It would be fun to get hooked up with them and at least attend the occasional talk or art show.
Thursday, November 17, 2005
Warp Drive Patented!
Okay, I know I'm blogging a bunch this week, and this seems more like a Friday afternoon thing than a real workday item, but I can't resist this one. Courtesy of Dave Farber's Interesting People list, we have the discovery of a fascinating patent issued by the USPTO on Nov. 1, 2005 to Boris Volfson.
Topic of patent #6,960,975? "Space Vehicle Propelled by the Pressure of Inflationary Vacuum State". A warp drive. Use 10,000 Tesla magnets and a 5meter shell of superconducting material, and you, too, can warp space and time, and travel at "a speed possibly approaching a local light-speed, the local light-speed which may be substantially higher than the light-speed in the ambient space"!
I wonder if this is the first patent for H.G. Wells' cavorite, the anti-gravity material in his novel The First Men in the Moon? (Volfson calls out the comparison directly.)
PDF and HTML versions of the patent available.
Topic of patent #6,960,975? "Space Vehicle Propelled by the Pressure of Inflationary Vacuum State". A warp drive. Use 10,000 Tesla magnets and a 5meter shell of superconducting material, and you, too, can warp space and time, and travel at "a speed possibly approaching a local light-speed, the local light-speed which may be substantially higher than the light-speed in the ambient space"!
I wonder if this is the first patent for H.G. Wells' cavorite, the anti-gravity material in his novel The First Men in the Moon? (Volfson calls out the comparison directly.)
PDF and HTML versions of the patent available.
Congratulations, Yoshi!
Yoshihisa Yamamoto, professor at Stanford and NII and world-renowned expert on quantum optics and various forms of quantum computing technology, received the Medal of Honor with Purple Ribbon yesterday, apparently from the emperor himself. Quite an honor, especially as Yoshi is among the younger recipients.
This is Getting Monotonous...
Another 4.8 off the coast of Ibaraki-ken. Figure this time is from Hi-net. The star is the most recent one, the rest are all activity in the last 24 hours. In the right-hand map, we live near the border between the two prefectures in the lower right, almost due north of the easternmost edge of Tokyo Bay. Shaking this time was pretty mild, you definitely wouldn't notice riding in a car or train and might not have even walking.
First Frost in Abiko and W in Kyoto
There's frost on the ground here in Abiko today, and even at 7:30 a.m. Narita Airport is reporting 2C as the temperature. The tree leaves this year are not very pretty, thanks to a sullen but not crisp October. Mikan and the many varieties of mushrooms are in season; I had a Chinese dish for lunch yesterday with maitake, which was a bit surprising. Fall is in full swing.
President Bush is Kyoto, visiting with Prime Minister Koizumi. Laura tried her hand at Japanese calligraphy, and the photo in the paper this morning looks like she caught on quickly.
There was a column in yesterday's Daily Yomiuri by a guy from the Heritage Foundation, who called the state of U.S.-Japan ties the best they've been in fifty years. That's pure spin, but it is true that they're pretty good right now. Bush and Koizumi seem to honestly like each other; their personalities are both swaggering cowboy. Except for beef, trade friction is low. Both are worried about the rise of China, both economically and militarily (environmentally should be a concern, too). Condi and Aso are in Pusan, working on North Korea. We're finishing up a reworking of the security deal. But, most important, Bush and Koizumi need each other. Japan is one of the biggest coalition partners in Iraq. Japan needs U.S. support for the permanent U.N. Security Council seat it so desparately wants.
It's not all smooth; Okinawa has an ambivalent relationship with the U.S. military, and the presence there is getting shuffled. The Okinawa governor took exception to Koizumi's remark that Japan must pay a "certain cost" to enjoy the security brought by the alliance. He correctly interprets that cost as Okinawa continuing to put up with our military.
President Bush is Kyoto, visiting with Prime Minister Koizumi. Laura tried her hand at Japanese calligraphy, and the photo in the paper this morning looks like she caught on quickly.
There was a column in yesterday's Daily Yomiuri by a guy from the Heritage Foundation, who called the state of U.S.-Japan ties the best they've been in fifty years. That's pure spin, but it is true that they're pretty good right now. Bush and Koizumi seem to honestly like each other; their personalities are both swaggering cowboy. Except for beef, trade friction is low. Both are worried about the rise of China, both economically and militarily (environmentally should be a concern, too). Condi and Aso are in Pusan, working on North Korea. We're finishing up a reworking of the security deal. But, most important, Bush and Koizumi need each other. Japan is one of the biggest coalition partners in Iraq. Japan needs U.S. support for the permanent U.N. Security Council seat it so desparately wants.
It's not all smooth; Okinawa has an ambivalent relationship with the U.S. military, and the presence there is getting shuffled. The Okinawa governor took exception to Koizumi's remark that Japan must pay a "certain cost" to enjoy the security brought by the alliance. He correctly interprets that cost as Okinawa continuing to put up with our military.
Wednesday, November 16, 2005
Magnitude 4.8 Wakeup Call
Am I a prophet, or what? (Mostly what, but I'm working on the prophet thang in case the academic gig falls through.)
At 6:18 this morning, magnitude 4.8 earthquake off the coast of Ibaraki-ken, 40km down. Here in Abiko, it was about shindo 2. Woke me up, sort of (usually I'm up before 6:00, but I worked until 1:00 last night). Not enough to get the adrenalin going, so I just rolled over and went back to sleep. My mother-in-law, who was walking between her house and ours, didn't even feel it.
This is at least the third from the same area and roughly the same size in the last month, and it seems like there has been one about every two weeks since we moved to Abiko in March. As long as it's releasing stress instead of building up, I'm happy.
Monday, November 14, 2005
3D Earthquake Info
While digging around for the last blog entry, I found a 3D VRML dataset of a year's worth of earthquakes under Japan. A couple of screen shots are above. You can see the subduction zone at the eastern edge of the isles extraordinarily clearly.
I'm using Firefox on Fedora Core 4 Linux. The FreeWRL FC3 RPM installed cleanly and works pretty well for VRML, but doesn't seem to do X3D properly. Be warned, this might take a couple of minutes to load; be patient.
The links:
This is a great use of 3D graphics.
Earthquake Info on Japan
My grandmother, whose ninetieth birthday is coming up soon, watches TV a lot, and calls my mom whenever there's an earthquake reported in Japan.
When there is an earthquake here, I check with tenki.jp, which is the government weather agency's website. Just above and to the right of the map is a pull-down menu of recent quake dates and times. The color-coded dots are the Japanese subjective shaking scale, which goes something like this:
- shindo 1: felt by sensitive people
- shindo 2: felt by many people
- shindo 3: wakeup call!
- shindo 4: pick up items previously precariously perched at higher levels
- shindo 5: call a handyman
- shindo 6: call a contractor
- shindo 7: call the army
Note that, although the numbers are similar, this is not the same as the magnitude of the earthquake; these numbers are what a person feels locally.
That info is filtered and takes a few (6-10) minutes to get posted. Hi-net is the direct access to the seismographic network.
Unfortunately, neither of those seems to have a decent English presence. I like tenki.jp because it has an i-mode interface, so when a quake hits in the middle of the night, I roll over, check my cell phone, then go back to sleep.
It does seem that we are having a lot of magnitude 4.0-5.3-ish quakes lately, mostly just north of us in Ibaraki-ken.
Sunday, November 13, 2005
Bigger Than a Breadbox, Smaller than a Football Stadium
[Second in the "practicalities of scalable quantum computers" series. The first installment was Forty Bucks a Qubit. Third is How Many Qubits Can Dance on the Head of a Pin?]
After talking to various people, I'm raising the target price on my quantum computer to a hundred million dollars. The U.S. government clearly spends that much on cluster supercomputers, though I don't think that they reached that level in the heyday of vector machines. BlueGene, for example, built by IBM, has 131,072 processors (65536 dual-core), and there's no way you're going to build a system like that, counting packaging, power, memory, storage, and networking, for less than a grand a processor (all these prices are ignoring physical plant, including the building).
Let's talk about packaging, cooling, and housing a semiconductor-based quantum computer. Even though we're talking about manipulating individual quanta, the space, power, thermal, and helium budgets for this are large. Helium? Yeah, helium. Both superconducting qubits and quantum dot qubits are operated at millikelvin temperatures, and the way you get there is by using a dilution refrigerator.
A dilution refrigerator, or dil fridge, uses the different condensation characteristics of helium-3 and helium-4 to cool things down to millikelvin temperatures. See the web pages here, here, and here, and the excellent PDF of the Hitchhiker's Guide to the Dilution Refrigerator from Charlie Marcus' lab at Harvard. All of the dil fridges I have ever seen are from Oxford Instruments.
Although there are a bunch of models, all the ones I've seen are almost two meters tall and a little under a meter in diameter, and you load your test sample in from the top on a long insert, so you need another two meters' clearance above (plus a small winch). A dil fridge is limited in theory to something like 7 millikelvin, and in practice to higher values depending on model. They can typically extract only a few hundred microwatts of heat from the device under test, which is limited to a few cubic centimeters. You're also going to need lots of clearance around the fridge, for operators, rack-mount equipment, and space to move equipment down the aisles. All this is by way of saying that you need quite a bit of space, power, and money for each setup. Let's call such a setup a "pod".
I'm considering the design of a quantum multicomputer, a set of quantum computing nodes interconnected via a quantum network. Let's start with one node per pod, and again set our target at a machine for factoring a 1,024-bit number. If we put, say, five application-level qubits per node, and add two levels of Steane [[7,1,3]] code, we've got 250 physical qubits per node, and 1,024 nodes in 1,024 pods. If each pod requires an area three meters square, we need an area about 100 meters by 100 meters for our total machine (bigger than a football field, smaller than a football stadium).
The thermal engineering is a serious problem. The electronics for each qubit currently fill a 19-inch rack, but a lot of that is measurement, not control, and of course in a production-engineered system we can increase the integration. It's still going to be a lot of equipmentfor 250 qubits, and worse, a lot more heat. It seems unlikely that our thermal budget will allow us to put the control electronics in the dil fridge (and some of it may not operate properly at such low temperatures, anyway). So, we're going to have to control it from outside. That means lots of signal lines - one per qubit for control, plus quite a few more (maybe as many as one per qubit) for measurement and various other things. Probably 4-500 microcoaxes that have to reach inside the fridge, each one carrying heat with it. Yow. Unless you substantially raise the extraction rate of the dil fridge, each line and measurement device is limited to about a microwatt - plus the heat that will leak through the fridge body itself. In the end it's almost certainly a multi-stage system, with parts running at room temperature, parts at liquid helium temps, and only the minimum necessary in the dil fridge itself.
Finally, we have to think about money again. We've just set a limit of about $100K per pod. I've never priced dil fridges, but I'd be surprised if they're cheaper than that (I wonder what kind of volume discount you get when you offer to buy a thousand dil fridges...), and we have a bunch of electronics and whatnot to pay for, in addition to the quantum computing device itself! We can do better on floor space and money if we can fit more than one node per pod, but doubling or quadrupling the number of coaxes and the heat budget is a daunting proposition on an already extremely aggressive engineering challenge.
It's not that I think this linear extrapolation from our current state is necessarily the way production systems will really be built (it's also worth noting that NMR, ion trap, optical lattice, and atom chip systems would require a completely different analysis). I'm trying to create a rough idea of the constraints we face and the problems that must be solved. One thing's for sure, though: when I found my quantum computing startup, world-class thermal and packaging engineers will be just as high on my shopping list as the actual quantum physicists.
After talking to various people, I'm raising the target price on my quantum computer to a hundred million dollars. The U.S. government clearly spends that much on cluster supercomputers, though I don't think that they reached that level in the heyday of vector machines. BlueGene, for example, built by IBM, has 131,072 processors (65536 dual-core), and there's no way you're going to build a system like that, counting packaging, power, memory, storage, and networking, for less than a grand a processor (all these prices are ignoring physical plant, including the building).
Let's talk about packaging, cooling, and housing a semiconductor-based quantum computer. Even though we're talking about manipulating individual quanta, the space, power, thermal, and helium budgets for this are large. Helium? Yeah, helium. Both superconducting qubits and quantum dot qubits are operated at millikelvin temperatures, and the way you get there is by using a dilution refrigerator.
A dilution refrigerator, or dil fridge, uses the different condensation characteristics of helium-3 and helium-4 to cool things down to millikelvin temperatures. See the web pages here, here, and here, and the excellent PDF of the Hitchhiker's Guide to the Dilution Refrigerator from Charlie Marcus' lab at Harvard. All of the dil fridges I have ever seen are from Oxford Instruments.
Although there are a bunch of models, all the ones I've seen are almost two meters tall and a little under a meter in diameter, and you load your test sample in from the top on a long insert, so you need another two meters' clearance above (plus a small winch). A dil fridge is limited in theory to something like 7 millikelvin, and in practice to higher values depending on model. They can typically extract only a few hundred microwatts of heat from the device under test, which is limited to a few cubic centimeters. You're also going to need lots of clearance around the fridge, for operators, rack-mount equipment, and space to move equipment down the aisles. All this is by way of saying that you need quite a bit of space, power, and money for each setup. Let's call such a setup a "pod".
I'm considering the design of a quantum multicomputer, a set of quantum computing nodes interconnected via a quantum network. Let's start with one node per pod, and again set our target at a machine for factoring a 1,024-bit number. If we put, say, five application-level qubits per node, and add two levels of Steane [[7,1,3]] code, we've got 250 physical qubits per node, and 1,024 nodes in 1,024 pods. If each pod requires an area three meters square, we need an area about 100 meters by 100 meters for our total machine (bigger than a football field, smaller than a football stadium).
The thermal engineering is a serious problem. The electronics for each qubit currently fill a 19-inch rack, but a lot of that is measurement, not control, and of course in a production-engineered system we can increase the integration. It's still going to be a lot of equipmentfor 250 qubits, and worse, a lot more heat. It seems unlikely that our thermal budget will allow us to put the control electronics in the dil fridge (and some of it may not operate properly at such low temperatures, anyway). So, we're going to have to control it from outside. That means lots of signal lines - one per qubit for control, plus quite a few more (maybe as many as one per qubit) for measurement and various other things. Probably 4-500 microcoaxes that have to reach inside the fridge, each one carrying heat with it. Yow. Unless you substantially raise the extraction rate of the dil fridge, each line and measurement device is limited to about a microwatt - plus the heat that will leak through the fridge body itself. In the end it's almost certainly a multi-stage system, with parts running at room temperature, parts at liquid helium temps, and only the minimum necessary in the dil fridge itself.
Finally, we have to think about money again. We've just set a limit of about $100K per pod. I've never priced dil fridges, but I'd be surprised if they're cheaper than that (I wonder what kind of volume discount you get when you offer to buy a thousand dil fridges...), and we have a bunch of electronics and whatnot to pay for, in addition to the quantum computing device itself! We can do better on floor space and money if we can fit more than one node per pod, but doubling or quadrupling the number of coaxes and the heat budget is a daunting proposition on an already extremely aggressive engineering challenge.
It's not that I think this linear extrapolation from our current state is necessarily the way production systems will really be built (it's also worth noting that NMR, ion trap, optical lattice, and atom chip systems would require a completely different analysis). I'm trying to create a rough idea of the constraints we face and the problems that must be solved. One thing's for sure, though: when I found my quantum computing startup, world-class thermal and packaging engineers will be just as high on my shopping list as the actual quantum physicists.
Thursday, November 10, 2005
NEC's Quantum Telephone
This posting is offline for the moment. Please send me email if you have questions or concerns.
[I have other postings on QKD at Stop the Myth and More on the Myth.]
[I have other postings on QKD at Stop the Myth and More on the Myth.]
Thursday, November 03, 2005
Forty Bucks a Qubit
First in a series of thoughts on what it means to build a scalable quantum computer... [Second installment is Bigger Than a Breadbox, Smaller Than a Football Stadium.]
My guess on the price at which the first production quantum computer is sold: forty bucks a qubit. Of course, the definition of "production" is fuzzy, but I mean a machine that is bought and installed for the purpose of solving real problems, not just a "let's support research" buy from the U.S. government. That is, it has to solve a problem that there's not a comparable classical solution for.
This guess is based on the assumption that the machine will be built to run Shor's factoring algorithm on a 1,024-bit number, which is sort of a questionable assumption, but we'll go with it (some physicists want them for direct simulation of complex Hamiltonians, but I don't understand that well enough to make any predictions there at all). That takes about five kilobits of application-level qubit space, and we'll multiply by fifty to support two levels of QEC. The [[7,1,3]] Steane code twice would be 49, but codes in production use are likely to be somewhat more efficient (maybe as good as 3:1, but I doubt much better), but there will no doubt be a need for additional space I didn't account for above, so we'll guess a quarter of a million physical qubits.
If you assume ten million U.S. dollars is a reasonable price for a machine with unique capabilities, that gives you forty bucks a qubit. I could easily be off by an order of magnitude in either direction, but I'll be very surprised if it's over a thousand dollars or under a buck.
Anyway, that's my prediction. What do you think? High? Low?
Next questions: what technology, and when?
I should put up a prediction at LongBets.org...
My guess on the price at which the first production quantum computer is sold: forty bucks a qubit. Of course, the definition of "production" is fuzzy, but I mean a machine that is bought and installed for the purpose of solving real problems, not just a "let's support research" buy from the U.S. government. That is, it has to solve a problem that there's not a comparable classical solution for.
This guess is based on the assumption that the machine will be built to run Shor's factoring algorithm on a 1,024-bit number, which is sort of a questionable assumption, but we'll go with it (some physicists want them for direct simulation of complex Hamiltonians, but I don't understand that well enough to make any predictions there at all). That takes about five kilobits of application-level qubit space, and we'll multiply by fifty to support two levels of QEC. The [[7,1,3]] Steane code twice would be 49, but codes in production use are likely to be somewhat more efficient (maybe as good as 3:1, but I doubt much better), but there will no doubt be a need for additional space I didn't account for above, so we'll guess a quarter of a million physical qubits.
If you assume ten million U.S. dollars is a reasonable price for a machine with unique capabilities, that gives you forty bucks a qubit. I could easily be off by an order of magnitude in either direction, but I'll be very surprised if it's over a thousand dollars or under a buck.
Anyway, that's my prediction. What do you think? High? Low?
Next questions: what technology, and when?
I should put up a prediction at LongBets.org...
Wednesday, November 02, 2005
Linux on a Vaio: CPU speed scaling
If you're looking for Fedora Core 6 (FC6) help, I've added a note here. (2006/11/7)
Random technical note for surfers looking for help...
[Request: this page gets a fair number of hits, but I'm not getting any feedback on it. If it doesn't have enough information to be useful to you, drop me a comment and let me know how I can make it better!]
I'm running Fedora Core 4 on a Sony Vaio type T laptop. One thing I never had working was CPU frequency scaling. One symptom was "error: no such device" during boot. If I tried it by hand, I got
My *guess* (not having read the code) is that the kernel dynamically attempts to figure out what your hardware is, and load the right kernel module. In my case, it was picking acpi-cpufreq, which is wrong, and so it was putting out a misleading error message. If it gets it right, I don't think you need a specific configuration step. If it can't figure it out, though, you need to add the "DRIVER=" line
to /etc/cpuspeed.conf. Here's my config, for a 900MHz Celeron M, which is apparently similar to a P4:
Once I did that, it all works well. Copy the above, and try uncommenting the different "DRIVER" lines until you find one that works.
/proc/acpi/processor/CPU0/throttling doesn't appear to correctly flag the current CPU speed, but there is lots of info in /sys/devices/system/cpu/cpu0/cpufreq/ that wasn't present before this module loaded correctly, such as
I added the CPU frequency monitor to my GNOME panel, and I see it scaling from 900MHz down to 112MHz pretty aggressively as the machine goes idle. I can't manually adjust the speed from that widget, like some people can, but I think that's because my monitor isn't running setuid.
My minimum power consumption now seems to be about 9.4 watts with the WLAN off, disk idle, CPU speed down, and screen brightness on minimum. That should be good enough for 5.5 hours, not too far off Sony's claim of 6 hours of battery life. Realistically, I was getting 4-4.5 before this change with mid-level screen brightness, we'll see if the CPU frquency scaling actually brings me benefits or not...
The one thing I'm still missing is that it comes out of sleep only slowly, and not very reliably.
Hope this helps someone.
Random technical note for surfers looking for help...
[Request: this page gets a fair number of hits, but I'm not getting any feedback on it. If it doesn't have enough information to be useful to you, drop me a comment and let me know how I can make it better!]
I'm running Fedora Core 4 on a Sony Vaio type T laptop. One thing I never had working was CPU frequency scaling. One symptom was "error: no such device" during boot. If I tried it by hand, I got
[root@pokhara sony_acpi]# pushd /lib/modules/2.6.13-1.1526_FC4/kernel/arch/i386/kernel/cpu/cpufreq/
/lib/modules/2.6.13-1.1526_FC4/kernel/arch/i386/kernel/cpu/cpufreq /home/rdv/linux/sony_acpi
[root@pokhara cpufreq]# ls
acpi-cpufreq.ko p4-clockmod.ko powernow-k8.ko speedstep-smi.ko
[root@pokhara cpufreq]# insmod acpi-cpufreq.ko
insmod: error inserting 'acpi-cpufreq.ko': -1 No such device
[root@pokhara cpufreq]#
My *guess* (not having read the code) is that the kernel dynamically attempts to figure out what your hardware is, and load the right kernel module. In my case, it was picking acpi-cpufreq, which is wrong, and so it was putting out a misleading error message. If it gets it right, I don't think you need a specific configuration step. If it can't figure it out, though, you need to add the "DRIVER=" line
to /etc/cpuspeed.conf. Here's my config, for a 900MHz Celeron M, which is apparently similar to a P4:
[rdv@pokhara dist-arch]$ cat /etc/cpuspeed.conf
VMAJOR=1
VMINOR=1
# uncomment this and set to the name of your CPUFreq module
#DRIVER="powernow-k7"
#DRIVER="acpi-cpufreq"
#DRIVER="powernow-k8"
#DRIVER="speedstep-smi"
DRIVER="p4-clockmod"
# Let background (nice) processes speed up the cpu
OPTS="$OPTS -n"
# Add your favorite options here
#OPTS="$OPTS -s 0 -i 10 -r"
# uncomment and modify this to check the state of the AC adapter
#OPTS="$OPTS -a /proc/acpi/ac_adapter/*/state"
# uncomment and modify this to check the system temperature
#OPTS="$OPTS -t /proc/acpi/thermal_zone/*/temperature 75"
Once I did that, it all works well. Copy the above, and try uncommenting the different "DRIVER" lines until you find one that works.
/proc/acpi/processor/CPU0/throttling doesn't appear to correctly flag the current CPU speed, but there is lots of info in /sys/devices/system/cpu/cpu0/cpufreq/ that wasn't present before this module loaded correctly, such as
[rdv@pokhara dist-arch]$ cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_available_frequencies
112500 225000 337500 450000 562500 675000 787500 900000
I added the CPU frequency monitor to my GNOME panel, and I see it scaling from 900MHz down to 112MHz pretty aggressively as the machine goes idle. I can't manually adjust the speed from that widget, like some people can, but I think that's because my monitor isn't running setuid.
My minimum power consumption now seems to be about 9.4 watts with the WLAN off, disk idle, CPU speed down, and screen brightness on minimum. That should be good enough for 5.5 hours, not too far off Sony's claim of 6 hours of battery life. Realistically, I was getting 4-4.5 before this change with mid-level screen brightness, we'll see if the CPU frquency scaling actually brings me benefits or not...
The one thing I'm still missing is that it comes out of sleep only slowly, and not very reliably.
Hope this helps someone.
Tuesday, November 01, 2005
Of Empresses, Shrines, Marines, and Universities: Japanese Politics
There has been a bunch of news lately, so I feel compelled to stick in just a short summary. Not a lot of commentary...
The U.S. and Japan are in the midst of reworking much of the bilateral security agreement. This may not make news in the U.S., but it's front page of the papers here every day for the last week or so. A few marines will move to Guam, one major Okinawa base will expand, and a lot of bases around Japan will shuffle. Okinawa is poor and very dependent on the U.S. armed forces for its economy, but friction over aircraft noise, accidents, barfights and rapes are constant. If memory serves, we have 40,000 armed forces personnel stationed here. America basically never withdraws from a country once we've settled in; we have bases in more than 100 countries around the world. In conjunction with the shuffle, Japan has agreed that a nuclear-powered aircraft carrier can be stationed at Yokosuka (south of Tokyo). Although a significant fraction of Japan's electricity is nuclear-generated, they have long objected to a nuclear-powered American ship here, but the Kitty Hawk, America's last non-nuclear aircraft carrier, is due to be retired soon. I think this is a proxy fight for whether or not the U.S. armed forces are allowed to have nuclear weapons on Japanese soil, which, as far as I can tell, is handled on a "don't ask, don't tell" basis.
Speaking of things war, the Yomiuri Shimbun recently commissioned a poll on responsibility for WWII. 67 percent said leaders of the Imperial Japanese Army or Navy followed by prime ministers (33), politicians (27), and Emperor Hirohito (19) (respondents were allowed to pick more than one answer). More interestingly, only 34 percent said that the wars against China and the U.S. were wars of aggression. The English-language Daily Yomiuri doesn't give the exact question or what the rest of the respondents thought, but that's an uncomfortably low number. Only 25 percent said their primary knowledge of WWII is through school; 34 percent said relatives (and the number of people with direct experience of the war is naturally declining rapidly). It's often said that the victors write the history, but in Japan, the losers got to write (or, in the case of schoolbooks, ignore) a big chunk of it, and nationalist politicians and right-wing organizations are still common.
The courts have issued a mixed bag of rulings recently on whether or not Prime Minister Koizumi's visits to Yasukuni Jinja, where 14 class-A war criminals and numerous minor ones are enshrined, violate the constitution's separation of church and state. At first glance, it seems odd; Bush led a prayer service after 9/11, after all. But this is really another proxy fight over opinions, contrition and responsibility for the war. China and South Korea get offended every time he goes, but in China's case, at least, it seems to be at least partially a calculated political attempt to keep their own people annoyed at the Japanese. Shinzo Abe, one of the candidates to succeed Koizumi next year when he steps down, has said he would continue the practice.
Koizumi shuffled his cabinet yesterday. Some of the current cabinet members have shifted political parties as many as five times in the last fifteen years; here parties seem to be much more about political fortunes and factions than about actual policy differences, with the exceptions of the minor communist and socialist parties. There are eighteen cabinet ministers, counting Koizumi, two of whom are women. There are profiles in today's paper, not complete but a few interesting facts. At least three seem to be sons or grandsons of former ministers, and two are former university professors. A breakdown of universities:
The cabinet includes a "state minister in charge of measures for declining birthrate and gender equality" (Inoguchi); I think the last two holders of this post have been women, though I'm unclear on how long it has been a cabinet post and whether it's a "woman's seat". There are two posts that seem to have some science and technology responsibility, "state minister for science, technology and IT policy" (Matsuda), and "education, science and technology minister" (Kosaka); I'm unclear on how responsibilities are divided up.
Speaking of women, the government is considering rewriting the laws governing imperial succession. At the moment, only a man can be emperor, but the current crown prince has only a daughter (Aiko, who is two). There is practically an Aiko cult here; the imperial family's privacy is guarded jealously, and when a short video of Aiko playing was released last winter, there were TV shows devoted to finding the manufacturers of the toys she was seen playing with. The debate is over whether succession should be oldest child, or whether a younger brother should take precedence over an older sister, or even if the emperor's younger brother should take precedence over the emperor's daughters. Japan has had women emperors, but not in many centuries.
Finally, the constitution here is being rewritten. The Liberal Democratic Party is trying to clarify the language around Japan's Self Defense Forces, allowing them to use force in international peacekeeping operations and even in defense of an ally (if you don't know, Japan's constitution currently renounces war as a right of the state in its famous "Article 9", which has always made the existence of the JSDF political ambiguous). The LDP will likely slip in some language designed to make Koizumi's visits to Yasukuni acceptable, too.
Anyway, interesting goings on here that can impact the entire international scene, but since many of them are policy wonk-ish issues, they probably aren't getting a lot of press elsewhere.
The U.S. and Japan are in the midst of reworking much of the bilateral security agreement. This may not make news in the U.S., but it's front page of the papers here every day for the last week or so. A few marines will move to Guam, one major Okinawa base will expand, and a lot of bases around Japan will shuffle. Okinawa is poor and very dependent on the U.S. armed forces for its economy, but friction over aircraft noise, accidents, barfights and rapes are constant. If memory serves, we have 40,000 armed forces personnel stationed here. America basically never withdraws from a country once we've settled in; we have bases in more than 100 countries around the world. In conjunction with the shuffle, Japan has agreed that a nuclear-powered aircraft carrier can be stationed at Yokosuka (south of Tokyo). Although a significant fraction of Japan's electricity is nuclear-generated, they have long objected to a nuclear-powered American ship here, but the Kitty Hawk, America's last non-nuclear aircraft carrier, is due to be retired soon. I think this is a proxy fight for whether or not the U.S. armed forces are allowed to have nuclear weapons on Japanese soil, which, as far as I can tell, is handled on a "don't ask, don't tell" basis.
Speaking of things war, the Yomiuri Shimbun recently commissioned a poll on responsibility for WWII. 67 percent said leaders of the Imperial Japanese Army or Navy followed by prime ministers (33), politicians (27), and Emperor Hirohito (19) (respondents were allowed to pick more than one answer). More interestingly, only 34 percent said that the wars against China and the U.S. were wars of aggression. The English-language Daily Yomiuri doesn't give the exact question or what the rest of the respondents thought, but that's an uncomfortably low number. Only 25 percent said their primary knowledge of WWII is through school; 34 percent said relatives (and the number of people with direct experience of the war is naturally declining rapidly). It's often said that the victors write the history, but in Japan, the losers got to write (or, in the case of schoolbooks, ignore) a big chunk of it, and nationalist politicians and right-wing organizations are still common.
The courts have issued a mixed bag of rulings recently on whether or not Prime Minister Koizumi's visits to Yasukuni Jinja, where 14 class-A war criminals and numerous minor ones are enshrined, violate the constitution's separation of church and state. At first glance, it seems odd; Bush led a prayer service after 9/11, after all. But this is really another proxy fight over opinions, contrition and responsibility for the war. China and South Korea get offended every time he goes, but in China's case, at least, it seems to be at least partially a calculated political attempt to keep their own people annoyed at the Japanese. Shinzo Abe, one of the candidates to succeed Koizumi next year when he steps down, has said he would continue the practice.
Koizumi shuffled his cabinet yesterday. Some of the current cabinet members have shifted political parties as many as five times in the last fifteen years; here parties seem to be much more about political fortunes and factions than about actual policy differences, with the exceptions of the minor communist and socialist parties. There are eighteen cabinet ministers, counting Koizumi, two of whom are women. There are profiles in today's paper, not complete but a few interesting facts. At least three seem to be sons or grandsons of former ministers, and two are former university professors. A breakdown of universities:
- Keio U.: 4 (Koizumi himself, Takenaka, Kosaka, Kawasaki)
- Tokyo U.: 3 (Chuma, Kutsukake, Yosano)
- Gakushuin U., "studied at Stanford and London School of Economics": 1 (Aso)
- Chuo U.: 1 (Nikai)
- Cairo U. (Egypt): 1 (Koike)
- Yale U. Ph.D. (U.S.) (undergrad unstated): 1 (Inoguchi)
- unstated: 7
The cabinet includes a "state minister in charge of measures for declining birthrate and gender equality" (Inoguchi); I think the last two holders of this post have been women, though I'm unclear on how long it has been a cabinet post and whether it's a "woman's seat". There are two posts that seem to have some science and technology responsibility, "state minister for science, technology and IT policy" (Matsuda), and "education, science and technology minister" (Kosaka); I'm unclear on how responsibilities are divided up.
Speaking of women, the government is considering rewriting the laws governing imperial succession. At the moment, only a man can be emperor, but the current crown prince has only a daughter (Aiko, who is two). There is practically an Aiko cult here; the imperial family's privacy is guarded jealously, and when a short video of Aiko playing was released last winter, there were TV shows devoted to finding the manufacturers of the toys she was seen playing with. The debate is over whether succession should be oldest child, or whether a younger brother should take precedence over an older sister, or even if the emperor's younger brother should take precedence over the emperor's daughters. Japan has had women emperors, but not in many centuries.
Finally, the constitution here is being rewritten. The Liberal Democratic Party is trying to clarify the language around Japan's Self Defense Forces, allowing them to use force in international peacekeeping operations and even in defense of an ally (if you don't know, Japan's constitution currently renounces war as a right of the state in its famous "Article 9", which has always made the existence of the JSDF political ambiguous). The LDP will likely slip in some language designed to make Koizumi's visits to Yasukuni acceptable, too.
Anyway, interesting goings on here that can impact the entire international scene, but since many of them are policy wonk-ish issues, they probably aren't getting a lot of press elsewhere.
Sunday, October 30, 2005
Tatopani: Hot Water Jazz in Roppongi, 11/24
(This posting is primarily for readers in the Tokyo area, but if you're into jazz, you might want to find the CDs anyway.)
Robbie Belgrade is a pal of mine. We met a couple of years ago on the way to Kodo's Earth Celebration. Robbie's a professional jazz musician, playing percussion and woodwinds. He studied tablas under Zakir Hussain, one of the most influential tablas players in the world.
Robbie's band Tatopani (which means "hot water" in Nepali) will be playing a release party for their new CD "Azure" in Roppongi on 11/24.
I haven't heard this particular band; like most jazz musicians, Robbie plays with many groups. The times I've heard him play have been quite enjoyable. The instrumentation is often very "world music"; in addition to Robbie's tablas, pandeiro and assorted percussion, the leader of Candela plays the shakuhachi (Japanese flute), for example, but the tunes are mostly pretty straight up jazz. Makes for pleasant sounds outside the usual tonal palette. The bands have been pretty tight, and the solos thoughtfully constructed (and sometimes humorous).
Tokyo, in general, is a good place to hear live jazz. Come out and support live music. Hope to see you there...
Robbie Belgrade is a pal of mine. We met a couple of years ago on the way to Kodo's Earth Celebration. Robbie's a professional jazz musician, playing percussion and woodwinds. He studied tablas under Zakir Hussain, one of the most influential tablas players in the world.
Robbie's band Tatopani (which means "hot water" in Nepali) will be playing a release party for their new CD "Azure" in Roppongi on 11/24.
I haven't heard this particular band; like most jazz musicians, Robbie plays with many groups. The times I've heard him play have been quite enjoyable. The instrumentation is often very "world music"; in addition to Robbie's tablas, pandeiro and assorted percussion, the leader of Candela plays the shakuhachi (Japanese flute), for example, but the tunes are mostly pretty straight up jazz. Makes for pleasant sounds outside the usual tonal palette. The bands have been pretty tight, and the solos thoughtfully constructed (and sometimes humorous).
Tokyo, in general, is a good place to hear live jazz. Come out and support live music. Hope to see you there...
Friday, October 28, 2005
MS+S2006: quantum computing conference in Japan
I just got a flier in the mail for MS+S2006, the International Symposium on Mesoscopic Superconductivity and Spintronics, sponsored by NTT and JST.
Sounds esoteric, but I went in 2004 (it's biannual), and about a third of the presentations and posters were explicitly quantum information processing, and at least another third were of some interest to QIP folks; last year the subtitle was even "In the light of quantum computation". (My paper was a somewhat abstract one on balancing quantum and classical computation, for example.)
It's a physics conference, so acceptances are based on abstracts submitted shortly before the conference, and many of the participants who aren't selected for the oral program present posters. The proceedings, with full papers, are published long after the conference. This all seems odd to those of us used to ACM and USENIX conferences, where full papers are reviewed, acceptance is extremely competitive for many of the conferences, and full proceedings are handed out at the conference itself.
NTT does an excellent job of hosting the conference, and I met a number of important researchers there (Martinis, Lloyd, Tsai, Nakamura, Mooij, to name a few); they get quite the list of attendees and speakers.
Abstracts due Jan. 23, conference Feb. 27-Mar. 2.
Anyway, consider coming, and I look forward to seeing you there!
Sounds esoteric, but I went in 2004 (it's biannual), and about a third of the presentations and posters were explicitly quantum information processing, and at least another third were of some interest to QIP folks; last year the subtitle was even "In the light of quantum computation". (My paper was a somewhat abstract one on balancing quantum and classical computation, for example.)
It's a physics conference, so acceptances are based on abstracts submitted shortly before the conference, and many of the participants who aren't selected for the oral program present posters. The proceedings, with full papers, are published long after the conference. This all seems odd to those of us used to ACM and USENIX conferences, where full papers are reviewed, acceptance is extremely competitive for many of the conferences, and full proceedings are handed out at the conference itself.
NTT does an excellent job of hosting the conference, and I met a number of important researchers there (Martinis, Lloyd, Tsai, Nakamura, Mooij, to name a few); they get quite the list of attendees and speakers.
Abstracts due Jan. 23, conference Feb. 27-Mar. 2.
Anyway, consider coming, and I look forward to seeing you there!
Wednesday, October 26, 2005
Bad News and Good News
No, nothing personal or professional - Bad News is the name of Tom Fenton's book. It's a rant about the decline of the media, especially broadcast news. It's a pretty good rant, but as a proposal for fixing the system, leaves a lot to be desired.
Fenton is a (now retired) foreign correspondent for CBS News. He's from the heyday of foreign correspondents - the 1970s - when money wasn't an object, and foreign correspondents were respected and enabled inside their organizations. He rants about all the usual suspects - the discovery that news can make money, the rise of the bean counters, sycophantic White House reporters, lazy reporters, dumb (or myopic) producers, and a public that would rather be entertained than informed.
Fenton believes, and I agree, that foreign news is incredibly important and that it's drastically underplayed in American media, even including the New York Times, but especially broadcast television news, which is where he spent his career. I also agree that there's no substitute for boots (or birkenstocks or galoshes or whatever foreign correspondents wear) on the ground, and that building an understanding of a culture takes time and effort - years, in fact, maybe decades.
But his proposed solution is backwards-looking. He mentions bloggers several times, talks about how laptops and DVD camcorders make filing reports from the field cheaper. But he demonstrates in his proposals that he Just Doesn't Get It about how completely the world has changed. I'm not talking about U.S. politics, geopolitics, or the news business, I'm talking about the technology.
I'm not totally enamored of all the things the brave new world we're creating bring us (see David Brin's Transparent Society), but I'm pretty certain that a great many of them are going to happen anyway. And most of the ones affecting news are going to be good (I've got a good rant on how narrowcasting means that the world doesn't appear the same to any two people, but we'll do that one another time). The problem is, Fenton has no particular plans to take advantage of anything but the most basic advances.
Fenton's proposals amount to, roughly, three things:
That's about it. None of them are bad things (and all have been tried, to one extent or another), but none of them demonstrate the least grasp of what is about to happen to media over the next decade or two.
For an extremely crude idea, see, say, the New York Times' coverage of Harriet Miers' nomination to the Supreme Court, or CNN's web site every day. Text stories, photos, multimedia slide shows with audio, video clips, and links to background data, both inside and outside their own websites. (Don't get me started ranting about proprietary data formats.)
Now project out a decade (don't put too much faith into that timeline). How about this:
It's six ten, and you sit down in your car to drive home (we'll assume one of those old-fashioned drive-it-yourself cars). It's a forty minute commute, and you always do the evening news. You don't sweat the fact that the broadcast started ten minutes ago, your in-car box time shifts. You get forty minutes of radio, pausing to take a phone call and replaying part of one story, so you only cover thirty minutes of the broadcast.
You pull into the driveway, go inside the house and start cooking dinner. The box in the kitchen offers to pick up where you left off on the radio broadcast and give you the last half hour, or go back and show you the video clips associated with the stories you heard in the car. You elect the video clips; the box plays them with abbreviated commentary, since it has kept track of what you've already heard. You take a couple of the offered backgrounders, getting several minutes on, say, the political flap over Koizumi's visits to Yasukuni Shrine back when China and Japan were rivals. Partway through, your spouse comes in with kids, so you switch it off.
After the kids are in bed, as you're getting ready for bed, you catch the last few minutes. You tell the box to compress down to five minutes, you're tired. It edits down several stories, including a brief update on one of the ones you heard earlier.
Would I commit an hour a day to media like that? You bet. I don't do much TV, but I probably spend better than an hour a day with the Daily Yomiuri and the New York Times, my two top sources.
Fenton needs to realize that the network news broadcast is an anachronism. It'll be gone before he cashes his first social security check. Here's what I think a news package delivered to the viewer needs:
There have been lots of other discussions on how searchable and customizable it has to be; I won't go into those. Nick Negroponte has been talking since the founding of the Media Lab about viewing a baseball game from the point of view of the baseball; toss that in, too.
What does a news organization need to provide this kind of content? A few tools, especially for creating the rich, variable depth. Nothing I don't expect to come along - advertisers will enjoy having that at least as much as news producers. Those are technical considerations, what about the people? A foreign correspondent is no longer the source of much original content, even today, let alone a decade from now, when raw footage will coming from everyone with a cell phone with a camera. What a foreign correspondent is is a guide to the torrent of available information. He or she organizes it, makes a story out of it, culls the important material, knows who the people are. That's what takes a truly broad and deep understanding of the issue at hand. Much of that work can, in theory, be done in London or New York, but you won't build the personal relationships and gut-level feel for the places, people and events without being there.
Anyway, just a few thoughts about the future of the news. Fenton has lots of worthwhile anecdotes on how sordid the behavior is on all sides of the Middle East and Central Asia theaters, but I'll leave those for another time, too.
Fenton is a (now retired) foreign correspondent for CBS News. He's from the heyday of foreign correspondents - the 1970s - when money wasn't an object, and foreign correspondents were respected and enabled inside their organizations. He rants about all the usual suspects - the discovery that news can make money, the rise of the bean counters, sycophantic White House reporters, lazy reporters, dumb (or myopic) producers, and a public that would rather be entertained than informed.
Fenton believes, and I agree, that foreign news is incredibly important and that it's drastically underplayed in American media, even including the New York Times, but especially broadcast television news, which is where he spent his career. I also agree that there's no substitute for boots (or birkenstocks or galoshes or whatever foreign correspondents wear) on the ground, and that building an understanding of a culture takes time and effort - years, in fact, maybe decades.
But his proposed solution is backwards-looking. He mentions bloggers several times, talks about how laptops and DVD camcorders make filing reports from the field cheaper. But he demonstrates in his proposals that he Just Doesn't Get It about how completely the world has changed. I'm not talking about U.S. politics, geopolitics, or the news business, I'm talking about the technology.
I'm not totally enamored of all the things the brave new world we're creating bring us (see David Brin's Transparent Society), but I'm pretty certain that a great many of them are going to happen anyway. And most of the ones affecting news are going to be good (I've got a good rant on how narrowcasting means that the world doesn't appear the same to any two people, but we'll do that one another time). The problem is, Fenton has no particular plans to take advantage of anything but the most basic advances.
Fenton's proposals amount to, roughly, three things:
- Recreate the foreign bureaus of the major news organizations.
- Build a grassroots organization that will monitor and push for quality of news reporting.
- Extend the nightly news to an hour, so there's room for in-depth reporting.
That's about it. None of them are bad things (and all have been tried, to one extent or another), but none of them demonstrate the least grasp of what is about to happen to media over the next decade or two.
For an extremely crude idea, see, say, the New York Times' coverage of Harriet Miers' nomination to the Supreme Court, or CNN's web site every day. Text stories, photos, multimedia slide shows with audio, video clips, and links to background data, both inside and outside their own websites. (Don't get me started ranting about proprietary data formats.)
Now project out a decade (don't put too much faith into that timeline). How about this:
It's six ten, and you sit down in your car to drive home (we'll assume one of those old-fashioned drive-it-yourself cars). It's a forty minute commute, and you always do the evening news. You don't sweat the fact that the broadcast started ten minutes ago, your in-car box time shifts. You get forty minutes of radio, pausing to take a phone call and replaying part of one story, so you only cover thirty minutes of the broadcast.
You pull into the driveway, go inside the house and start cooking dinner. The box in the kitchen offers to pick up where you left off on the radio broadcast and give you the last half hour, or go back and show you the video clips associated with the stories you heard in the car. You elect the video clips; the box plays them with abbreviated commentary, since it has kept track of what you've already heard. You take a couple of the offered backgrounders, getting several minutes on, say, the political flap over Koizumi's visits to Yasukuni Shrine back when China and Japan were rivals. Partway through, your spouse comes in with kids, so you switch it off.
After the kids are in bed, as you're getting ready for bed, you catch the last few minutes. You tell the box to compress down to five minutes, you're tired. It edits down several stories, including a brief update on one of the ones you heard earlier.
Would I commit an hour a day to media like that? You bet. I don't do much TV, but I probably spend better than an hour a day with the Daily Yomiuri and the New York Times, my two top sources.
Fenton needs to realize that the network news broadcast is an anachronism. It'll be gone before he cashes his first social security check. Here's what I think a news package delivered to the viewer needs:
- It must work across all media - text, images, sound, video - and all viewing and delivery platforms - HDTV, cell phone video, cell phone audio, PDA text, car radio. (Call this variable width, if you like.)
- It has to retain context as you move from box to box (car radio to kitchen TV) and session to session (e.g., updates without repeating the whole story the next morning).
- It has to offer variable depth; the same story should be available in one-, three-, and ten-minute formats. Creating and managing this variable depth is critical and difficult.
- It has to offer still more depth, including the provenance of all of the data, access to multiple viewpoints on the same events, multiple translations of foreign-language text and speech, as well as the originals. For edited video of, say, a riot, the fifteen seconds shown in the organized report should link back to the hour of raw footage in a useful fashion.
There have been lots of other discussions on how searchable and customizable it has to be; I won't go into those. Nick Negroponte has been talking since the founding of the Media Lab about viewing a baseball game from the point of view of the baseball; toss that in, too.
What does a news organization need to provide this kind of content? A few tools, especially for creating the rich, variable depth. Nothing I don't expect to come along - advertisers will enjoy having that at least as much as news producers. Those are technical considerations, what about the people? A foreign correspondent is no longer the source of much original content, even today, let alone a decade from now, when raw footage will coming from everyone with a cell phone with a camera. What a foreign correspondent is is a guide to the torrent of available information. He or she organizes it, makes a story out of it, culls the important material, knows who the people are. That's what takes a truly broad and deep understanding of the issue at hand. Much of that work can, in theory, be done in London or New York, but you won't build the personal relationships and gut-level feel for the places, people and events without being there.
Anyway, just a few thoughts about the future of the news. Fenton has lots of worthwhile anecdotes on how sordid the behavior is on all sides of the Middle East and Central Asia theaters, but I'll leave those for another time, too.
Saturday, October 22, 2005
The Scariest Thing I've Ever Read
Just in time for Halloween...
Stephen King called The Hot Zone "one of the most horrifying things I've ever read." I would hand that title instead to David Goodstein's Out of Gas (he has also lectured on this topic; you can get RealVideo here). Goodstein's concern is not the possible deaths of millions of people due to Ebola and Marburg. It's not the Bush administration paving over Yosemite. It's not even anthropogenic global warming and a piddling few degrees' increase in average temperatures. He's worried about whether or not we will run out of fossil fuels before we figure out how to live sustainably, and consequently whether civilization as we know it will come to an end.
Goodstein is a physics professor at Caltech. In the book, he heads straight for the basics: we're consuming energy that was stored in the ground long ago. We are consuming it far faster than it replenishes itself. It will run out; what are we to do when it does?
Goodstein covers the well-known Hubbert peak, and suggests that we are now at the world-wide peak of petroleum production, give or take a decade or so. When we hit that peak, we are about half way done with the amount of oil we can successfully extract and use. But that doesn't mean we have another 150 years to go before problems occur; because demand is increasing and production is flat to declining as we pass the peak, serious shortages are likely to begin within a decade or two at most. Such shortages will lead to price instability, and are especially problematic since petroleum is such a flexible, useful material. We use it in plastics, fertilizers, and more, as well as burning the stuff directly, so a shortage has the potential to threaten such fundamental societal requirements as food production.
He discusses where oil comes from, how inefficient it is to use oil shale, how natural gas, coal, and even accessible supplies of fissionable uranium will run out, and relatively soon. Each of those supplies is worth a few decades, given reasonable projections about population growth, energy consumption, and the fraction of the resource that is recoverable at reasonable economic and thermodynamic returns. All told, if we are flexible enough about our fuels, we have maybe until the end of the century. Then what?
Our only choice is fusion. We can either get our energy indirectly, by creating solar cells that ultimately derive the power they deliver from the sun's fusion, or we can figure out how to run fusion here on earth - but we haven't been very successful at that yet.
What to do, what to do?
Stephen King called The Hot Zone "one of the most horrifying things I've ever read." I would hand that title instead to David Goodstein's Out of Gas (he has also lectured on this topic; you can get RealVideo here). Goodstein's concern is not the possible deaths of millions of people due to Ebola and Marburg. It's not the Bush administration paving over Yosemite. It's not even anthropogenic global warming and a piddling few degrees' increase in average temperatures. He's worried about whether or not we will run out of fossil fuels before we figure out how to live sustainably, and consequently whether civilization as we know it will come to an end.
Goodstein is a physics professor at Caltech. In the book, he heads straight for the basics: we're consuming energy that was stored in the ground long ago. We are consuming it far faster than it replenishes itself. It will run out; what are we to do when it does?
Goodstein covers the well-known Hubbert peak, and suggests that we are now at the world-wide peak of petroleum production, give or take a decade or so. When we hit that peak, we are about half way done with the amount of oil we can successfully extract and use. But that doesn't mean we have another 150 years to go before problems occur; because demand is increasing and production is flat to declining as we pass the peak, serious shortages are likely to begin within a decade or two at most. Such shortages will lead to price instability, and are especially problematic since petroleum is such a flexible, useful material. We use it in plastics, fertilizers, and more, as well as burning the stuff directly, so a shortage has the potential to threaten such fundamental societal requirements as food production.
He discusses where oil comes from, how inefficient it is to use oil shale, how natural gas, coal, and even accessible supplies of fissionable uranium will run out, and relatively soon. Each of those supplies is worth a few decades, given reasonable projections about population growth, energy consumption, and the fraction of the resource that is recoverable at reasonable economic and thermodynamic returns. All told, if we are flexible enough about our fuels, we have maybe until the end of the century. Then what?
Our only choice is fusion. We can either get our energy indirectly, by creating solar cells that ultimately derive the power they deliver from the sun's fusion, or we can figure out how to run fusion here on earth - but we haven't been very successful at that yet.
What to do, what to do?
Friday, October 14, 2005
More on the Myth
Okay, this one's not really about Shor and QKD, but it is about the authenticated channel for QKD.
I said the physicists underplayed the importance of the authenticated channel in operational practice, and was (rightly) chastened by Dave Bacon and Daniel Gottesman. In the interests of equal time, here's proof that not everyone in the computer networking community gets it:
A thread on an Internet Draft (= proposed RFC) on using QKD for key exchange for PPP. Here's a link to the Internet Draft itself (warning, that link will probably go stale in April 2006, and may or may not properly track revisions to the draft, depending on whether or not I picked up the right link). The email thread seems a little fragmented, part of the conversation appears to be taking place elsewhere.
I haven't actually read the draft (the "view document" link at the IETF site appears broken?!?), but from the email thread, it appears that Mr. Sfaxi either does not understand or cannot explain the use of the classical authenticated channel. Remember, gang: QKD requires access to an authenticated classical channel.
Stay tuned for more late-breaking news from the exciting world of IETF...
[I've you've just come into this conversation, I recommend reading this posting, this posting, and especially quant-ph/0406147.]
I said the physicists underplayed the importance of the authenticated channel in operational practice, and was (rightly) chastened by Dave Bacon and Daniel Gottesman. In the interests of equal time, here's proof that not everyone in the computer networking community gets it:
A thread on an Internet Draft (= proposed RFC) on using QKD for key exchange for PPP. Here's a link to the Internet Draft itself (warning, that link will probably go stale in April 2006, and may or may not properly track revisions to the draft, depending on whether or not I picked up the right link). The email thread seems a little fragmented, part of the conversation appears to be taking place elsewhere.
I haven't actually read the draft (the "view document" link at the IETF site appears broken?!?), but from the email thread, it appears that Mr. Sfaxi either does not understand or cannot explain the use of the classical authenticated channel. Remember, gang: QKD requires access to an authenticated classical channel.
Stay tuned for more late-breaking news from the exciting world of IETF...
[I've you've just come into this conversation, I recommend reading this posting, this posting, and especially quant-ph/0406147.]
Thursday, October 13, 2005
Quantum Time Machines: What? Why? and (maybe) How?
Tim Ralph is in Tokyo this week, and is giving a talk today. Here's
the abstract:
Title: Quantum Time Machines: What? Why? and (maybe) How?
Abstract:
Whether time travel into the past is possible is an undecided physical
question [1]. Recently it has been noted that certain models of time
travel for quantum particles do not lead to the same difficult
paradoxes that arise for classical particles [2]. Furthermore the
types of quantum evolutions predicted for these "quantum time
machines" could give rise to a "super" quantum computer, able to solve
problems thought to be intractable by any other means [3]. In this
talk I will discuss time machines in general, how quantum mechanics
avoids the paradoxes and the unusual evolutions predicted. I will
then argue that the requirements for realizing such machines are not
as stringent as previously thought and I will propose "horizon
technology" experiments which could test these ideas [4].
With an abstract like that, you'd have to beat with me a stick to keep me away from the talk. Now, I only know a little about relativity - what every Caltech freshman knows (special relativity) and any fan of popular science writing knows (e.g., Kip Thorne's fabulous Black Holes and Time Warps). I know squat about the real math of general relativity, but I'm familiar with the basic implications of the curvature of space, black holes, wormholes, etc. So, should be a fun but challenging talk.
To prepare, I spent a little time this morning reading Tim's paper (quant-ph/0510038) and took a quick look at Dave Bacon's recent paper. Dave's paper is apparently a pretty major one. Building on work by Deutsch, Brun, and others, he shows that the existence of closed timelike curves (CTCs) would allow NP-complete problems to be solved on a quantum computer using only polynomial resources.
What the heck is a closed timelike curve? It's a path through a wormhole that comes back to where you started. Special relativity treats space and time as a four-dimensional space called spacetime, and establishes rules for paths in that space. You can never reach another point in spacetime that would require you to travel faster than light to get there. General relativity, which introduces the curvature of space, in its extreme appears to allow the creation of wormholes - places in space that, if you step through, take you to another distant point in space. Travelling through a wormhole can allow you to travel into your own past, coming back to where you started, and creating a "closed timelike curve". So Dave showed that travelling through a wormhole will allow you to solve NP-complete problems efficiently on a quantum computer. (We won't talk about grandfather paradoxes and the like, but apparently quantum mechanics helps there.)
Moving on, Tim's paper is lucid and remarkably easy to read for a non-specialist like me. He shows that you can take an entangled pair of quanta (an EPR pair), relativistically accelerate one and bring it back to the starting point, and like the pedagogical twins, one particle will now be "older" than the other. Using the standard quantum techniques of teleportation, he then creates a state that's something a little like a wormhole, essentially a loop in time. You can't use this to violate causality or learn about the future, but it does allow nonlinear evolution of the quantum system. Dave's system depends on the nonlinearity created by the wormhole; here Tim has done it without one. Fascinating.
Okay, time to pack up and head to the seminar and see whether I've correctly interpreted Tim, and what other features of this there are that I haven't thought of...
(From this point, it's just the notes I typed during the seminar, so apologies if they seem a little abrupt or semi-coherent.)
Morris, Thorne, Yurtsever, PRL 61
Where are all the time tourists? There's a plaque in Perth that says, "In the event that the transportation of life from the future" becomes possible, please show up at March 31, 2005, in Perth. No one did. (Reminds me of the MIT conference.) Requiring that a time machine receiver be built first eliminates the problem of the lack of visible travellers, but still doesn't eliminate the standard causality problems.
Tim actually likes Sagan's Contact. Wormholes were developed by Einstein and Rosen, so they are also called Einstein-Rosen bridges, but in their solution the wormhole collapses too quickly to be used. Kip Thorne showed that if you thread a wormhole with exotic matter, it might stay open long enough to let regular matter pass through. Thorne showed that many of the possible paradoxes resolve themselves, but whether they all resolve comfortably is unknown.
You get a nice little paradox if you use classical bits and a CNOT gate. Start with a one on the target bit, run it through the CNOT gate, and take that output rho, shove it through your time machine into the past, then use that as the control line for the CNOT gate. There's no possible consistent result. (Think about the states where rho comes out of the time machine as a one or a zero.)
However, if you do this with qubits, there is a solution. rho = 1/2(|0><0| + |1><1|) works. Deutsch then generalized and showed that any unitary evolution U has a solution without creating classical paradoxes, provided that you keep your particle that goes through the wormhole in a box and neither measure nor prepare it during the time travel interval.
The wormhole introduces a nonlinearity. Non-relativistic ("classical") quantum mechanics, of course, is linear. So is there a way to use that nonlinearity now added? Yes, in certain regions, it creates a faster growth of the trace distance between two states. This is where the power comes from that Bacon used to solve NP-complete problems.
Of course, we don't have a source of wormholes to experiment with, and don't even know how to build them. So what about a stochastic time machine? One that lights up one of four possible lights (labeled I, X, Z, and XZ) every time you shove a particle into to send it into the past. If you're familiar with quantum teleportation, you'll immediately recognize those as the operators you need to apply to retrieve the teleported state, once you've measured the qubit at the source.
During the time travel interval (between the past time where you receive the particle, and the future time where you sent it), what you have is a mixed state. Now there are no paradoxes, even if you observe the particle. And you can compute with it. But your real, true final answer isn't known until after the (local) time that you sent the particle into the time machine.
Teleportation can be considered a "stochastic wormhole". Do the same thing you would with a real wormhole - accelerate one of the particles at relativistic speeds for a while, then bring it back where you started - and you have a stochastic time machine.
What does it all mean? It seems that quantum systems are better behaved with respect to time travel than classical machines. A stochastic quantum time machine still leads to interesting and potentially useful quantum evolutions whilst avoiding ad hoc assumptions. Teleportation using time displaced entanglement appears equivalent to a stochastic time machine. These experiments are hard, but not too hard.
Question:What does increasing the overlap do to security proofs of QKD and things of that nature? Answer:Don't know. Would be interesting to check...
Question:Increasing the overlap, doesn't that have implications for cloning and superluminal communication? Answer:You essentially "lose contact" with other qubits (you have to trace out over other qubits, because the operation is on the reduced density operator). So, no, you don't get superluminal. (See Deutsch.)
It startles and intrigues me no end that quantum mechanics, information theory, and general relativity converge in such interesting ways.
See this auction!
the abstract:
Speaker: Prof.Tim C. Ralph
Centre for Quantum Computer Technology,
University of Queensland,
Australia.
Title: Quantum Time Machines: What? Why? and (maybe) How?
Abstract:
Whether time travel into the past is possible is an undecided physical
question [1]. Recently it has been noted that certain models of time
travel for quantum particles do not lead to the same difficult
paradoxes that arise for classical particles [2]. Furthermore the
types of quantum evolutions predicted for these "quantum time
machines" could give rise to a "super" quantum computer, able to solve
problems thought to be intractable by any other means [3]. In this
talk I will discuss time machines in general, how quantum mechanics
avoids the paradoxes and the unusual evolutions predicted. I will
then argue that the requirements for realizing such machines are not
as stringent as previously thought and I will propose "horizon
technology" experiments which could test these ideas [4].
[1] M.S.Morris, K.P.Thorne and U.Yurtsever, Phys.Rev.Lett.61, 1446 (1988).
[2] D.Deutsch, Phys.Rev.D 44, 3197 (1991).
[3] D.Bacon, Phys.Rev.A, 70, 032309 (2004).
[4] T.C.Ralph, quant-ph/0510038.
With an abstract like that, you'd have to beat with me a stick to keep me away from the talk. Now, I only know a little about relativity - what every Caltech freshman knows (special relativity) and any fan of popular science writing knows (e.g., Kip Thorne's fabulous Black Holes and Time Warps). I know squat about the real math of general relativity, but I'm familiar with the basic implications of the curvature of space, black holes, wormholes, etc. So, should be a fun but challenging talk.
To prepare, I spent a little time this morning reading Tim's paper (quant-ph/0510038) and took a quick look at Dave Bacon's recent paper. Dave's paper is apparently a pretty major one. Building on work by Deutsch, Brun, and others, he shows that the existence of closed timelike curves (CTCs) would allow NP-complete problems to be solved on a quantum computer using only polynomial resources.
What the heck is a closed timelike curve? It's a path through a wormhole that comes back to where you started. Special relativity treats space and time as a four-dimensional space called spacetime, and establishes rules for paths in that space. You can never reach another point in spacetime that would require you to travel faster than light to get there. General relativity, which introduces the curvature of space, in its extreme appears to allow the creation of wormholes - places in space that, if you step through, take you to another distant point in space. Travelling through a wormhole can allow you to travel into your own past, coming back to where you started, and creating a "closed timelike curve". So Dave showed that travelling through a wormhole will allow you to solve NP-complete problems efficiently on a quantum computer. (We won't talk about grandfather paradoxes and the like, but apparently quantum mechanics helps there.)
Moving on, Tim's paper is lucid and remarkably easy to read for a non-specialist like me. He shows that you can take an entangled pair of quanta (an EPR pair), relativistically accelerate one and bring it back to the starting point, and like the pedagogical twins, one particle will now be "older" than the other. Using the standard quantum techniques of teleportation, he then creates a state that's something a little like a wormhole, essentially a loop in time. You can't use this to violate causality or learn about the future, but it does allow nonlinear evolution of the quantum system. Dave's system depends on the nonlinearity created by the wormhole; here Tim has done it without one. Fascinating.
Okay, time to pack up and head to the seminar and see whether I've correctly interpreted Tim, and what other features of this there are that I haven't thought of...
(From this point, it's just the notes I typed during the seminar, so apologies if they seem a little abrupt or semi-coherent.)
Morris, Thorne, Yurtsever, PRL 61
Where are all the time tourists? There's a plaque in Perth that says, "In the event that the transportation of life from the future" becomes possible, please show up at March 31, 2005, in Perth. No one did. (Reminds me of the MIT conference.) Requiring that a time machine receiver be built first eliminates the problem of the lack of visible travellers, but still doesn't eliminate the standard causality problems.
Tim actually likes Sagan's Contact. Wormholes were developed by Einstein and Rosen, so they are also called Einstein-Rosen bridges, but in their solution the wormhole collapses too quickly to be used. Kip Thorne showed that if you thread a wormhole with exotic matter, it might stay open long enough to let regular matter pass through. Thorne showed that many of the possible paradoxes resolve themselves, but whether they all resolve comfortably is unknown.
You get a nice little paradox if you use classical bits and a CNOT gate. Start with a one on the target bit, run it through the CNOT gate, and take that output rho, shove it through your time machine into the past, then use that as the control line for the CNOT gate. There's no possible consistent result. (Think about the states where rho comes out of the time machine as a one or a zero.)
However, if you do this with qubits, there is a solution. rho = 1/2(|0><0| + |1><1|) works. Deutsch then generalized and showed that any unitary evolution U has a solution without creating classical paradoxes, provided that you keep your particle that goes through the wormhole in a box and neither measure nor prepare it during the time travel interval.
The wormhole introduces a nonlinearity. Non-relativistic ("classical") quantum mechanics, of course, is linear. So is there a way to use that nonlinearity now added? Yes, in certain regions, it creates a faster growth of the trace distance between two states. This is where the power comes from that Bacon used to solve NP-complete problems.
Of course, we don't have a source of wormholes to experiment with, and don't even know how to build them. So what about a stochastic time machine? One that lights up one of four possible lights (labeled I, X, Z, and XZ) every time you shove a particle into to send it into the past. If you're familiar with quantum teleportation, you'll immediately recognize those as the operators you need to apply to retrieve the teleported state, once you've measured the qubit at the source.
During the time travel interval (between the past time where you receive the particle, and the future time where you sent it), what you have is a mixed state. Now there are no paradoxes, even if you observe the particle. And you can compute with it. But your real, true final answer isn't known until after the (local) time that you sent the particle into the time machine.
Teleportation can be considered a "stochastic wormhole". Do the same thing you would with a real wormhole - accelerate one of the particles at relativistic speeds for a while, then bring it back where you started - and you have a stochastic time machine.
What does it all mean? It seems that quantum systems are better behaved with respect to time travel than classical machines. A stochastic quantum time machine still leads to interesting and potentially useful quantum evolutions whilst avoiding ad hoc assumptions. Teleportation using time displaced entanglement appears equivalent to a stochastic time machine. These experiments are hard, but not too hard.
Question:What does increasing the overlap do to security proofs of QKD and things of that nature? Answer:Don't know. Would be interesting to check...
Question:Increasing the overlap, doesn't that have implications for cloning and superluminal communication? Answer:You essentially "lose contact" with other qubits (you have to trace out over other qubits, because the operation is on the reduced density operator). So, no, you don't get superluminal. (See Deutsch.)
It startles and intrigues me no end that quantum mechanics, information theory, and general relativity converge in such interesting ways.
See this auction!
Friday, October 07, 2005
My First Perpetual-Motion Machine
A totally random anecdote...last night I recalled building my first perpetual motion machine. I don't have a clear idea of how old I was, but old enough to have my electronics science kit, including a small solar cell. Ten, perhaps?
My dad is big on O-gauge model trains, and they were set up in the basement. There were some lampposts with grain-of-wheat lightbulbs to go with it. The lampposts were intended to be battery-driven, but I had a better idea: I'd run them with my solar cell. I realized that they would need to be "primed"; I'd have to start with the battery hooked up, but then assuming all went well, I could unplug the battery and the solar cell would take over. Light from the lampposts themselves would drive the solar cell, which would drive the lampposts. Viola! Lighting for the trains, without a battery!
Needless to say, every time I unplugged the battery, the lampposts went out. I was smart enough to figure out that the solar cell needed more light, so I tried adding reflectors that would send back a greater percentage of the light to the solar cell. No joy. I think (though this part of the recollection is fuzzy) that I wound up trying a less ambitious system, with just the lightbulb directly in front of the solar cell, which of course failed, too.
And there this particular memory vignette fades to black. I have no particular recollection of realizing that what I was trying was theoretically impossible, only that the practical considerations were insurmountable. There were, in all probability, mechanical perpetual motion machines from about the same time frame. Something for me to try to dig out of that unreliable and fast-fading bank...
My dad is big on O-gauge model trains, and they were set up in the basement. There were some lampposts with grain-of-wheat lightbulbs to go with it. The lampposts were intended to be battery-driven, but I had a better idea: I'd run them with my solar cell. I realized that they would need to be "primed"; I'd have to start with the battery hooked up, but then assuming all went well, I could unplug the battery and the solar cell would take over. Light from the lampposts themselves would drive the solar cell, which would drive the lampposts. Viola! Lighting for the trains, without a battery!
Needless to say, every time I unplugged the battery, the lampposts went out. I was smart enough to figure out that the solar cell needed more light, so I tried adding reflectors that would send back a greater percentage of the light to the solar cell. No joy. I think (though this part of the recollection is fuzzy) that I wound up trying a less ambitious system, with just the lightbulb directly in front of the solar cell, which of course failed, too.
And there this particular memory vignette fades to black. I have no particular recollection of realizing that what I was trying was theoretically impossible, only that the practical considerations were insurmountable. There were, in all probability, mechanical perpetual motion machines from about the same time frame. Something for me to try to dig out of that unreliable and fast-fading bank...
Tuesday, October 04, 2005
100 Greatest Americans?
Rod & Ted's Alternate List of Greatest Americans
After reading the Discovery Channel's list of one hundred candidates for the Greatest American, Ted and I spent way too much time on creating our own version. We wound up throwing out more than half of the original list.
There was significant discussion over whether athletes and entertainers belonged on the list at all. They were certainly FAR over-represented in the original list. Probably none would be serious candidates for the single greatest American -- but the list of true candidates for that honor is very short, anyway. We settled on keeping representatives from almost the whole range of human endeavor. Most of the athletes, artists, musicians, and film actors/directors we kept were truly transformative, in our opinion. Feel free to argue!
Fields that we felt were egregiously underrepresented in the original list were writers, artists, jurists, scientists and engineers. In our current list, it's possible that business types are underrepresented. We wanted an educator, but couldn't come up with one.
In a few cases, we invoked executive privilege and listed two or three people as a single entry, when their names are rarely mentioned apart (or, in the case of Apollo 11, should be).
In a *very* few cases, the person in question is a putz. But, we felt their accomplishments were difficult to ignore, and in at least two cases, their putziness came into evidence later in life, after their accomplishments had already established their importance.
For your reading and arguing pleasure.
Keep (44):
New (51):
* = putz, but...
Our breakdown for the whole 100, by profession (totals exceed 100 because our list is actually slightly over 100, and some have two professions):
Eliminate (56):
Honorable Mentions:
After reading the Discovery Channel's list of one hundred candidates for the Greatest American, Ted and I spent way too much time on creating our own version. We wound up throwing out more than half of the original list.
There was significant discussion over whether athletes and entertainers belonged on the list at all. They were certainly FAR over-represented in the original list. Probably none would be serious candidates for the single greatest American -- but the list of true candidates for that honor is very short, anyway. We settled on keeping representatives from almost the whole range of human endeavor. Most of the athletes, artists, musicians, and film actors/directors we kept were truly transformative, in our opinion. Feel free to argue!
Fields that we felt were egregiously underrepresented in the original list were writers, artists, jurists, scientists and engineers. In our current list, it's possible that business types are underrepresented. We wanted an educator, but couldn't come up with one.
In a few cases, we invoked executive privilege and listed two or three people as a single entry, when their names are rarely mentioned apart (or, in the case of Apollo 11, should be).
In a *very* few cases, the person in question is a putz. But, we felt their accomplishments were difficult to ignore, and in at least two cases, their putziness came into evidence later in life, after their accomplishments had already established their importance.
For your reading and arguing pleasure.
Keep (44):
- Ali, Muhammad (a)
- Angelou, Maya (w)
- Anthony, Susan B. (l)
- Bell, Alexander Graham (i)
- Carnegie, Andrew (b)
- Carson, Johnny (f)
- Carver, George Washington (i)
- Chavez, Cesar (l)
- Disney, Walt (f,v,b)
- Douglass, Frederick (l)
- Edison, Thomas Alva (i)
- Einstein, Albert (i)
- Ford, Henry (b)
- Franklin, Benjamin (i,t)
- Gates, Bill (b)
- Glenn, John (e,t)
- Graham, Billy (r)
- Hamilton, Alexander (t)
- Jefferson, Thomas (pr,i)
- Keller, Helen (l)
- Kennedy, John F. (p)
- King Jr., Dr. Martin Luther (l)
- Lincoln, Abraham (p)
- Lindbergh, Charles (e)
- Malcolm X (l)
- Murphy, Audie (s)
- Owens, Jesse (a)
- Patton, George (s)
- Presley, Elvis (m)
- Roebling, John A. ?
- Robinson, Jackie (a)
- Roosevelt, Franklin D (p)
- Roosevelt, Theodore (p)
- Ruth, Babe (a)
- Salk, Jonas (i)
- Smith, Joseph (r)
- Tesla, Nikola (i)
- Tubman, Harriet (l)
- Twain, Mark (w)
- Washington, George (s,p)
- Wayne, John (f)
- Wright, Orville & Wilbur (i)
- Yeager, Chuck (e)
New (51):
- Ansel Adams (v)
- Apollo 11 crew (Neil Armstrong, Buzz Aldrin, & Michael Collins) (e)
- Louis Armstrong (m)
- Daniel Boone (e)
- Ray Bradbury (w)
- William Jennings Bryan (j)
- Alexander Calder (v)
- Johnny Cash (m)
- Vint Cerf (i)
- Edward Drinker Cope & Othniel Charles Marsh (i)
- Aaron Copland (m)
- Davy Crockett (e)
- Walter Cronkite (f)
- Glenn Curtiss (i,b)
- Virginia Dare (o)
- Clarence Darrow (j)
- Charles & Ray Eames (v)
- Richard Feynman (i)
- Bobby Fischer * (o)
- F. Scott Fitzgerald (w)
- Robert Fulton (i)
- Theodore Giesel (w)
- William Randolph Hearst (b)
- Ernest Hemingway (w)
- Sam Houston (e,s,t)
- Edwin Hubble (i)
- Andrew Jackson (s,p)
- Francis Scott Key (w)
- Meriwether Lewis & William Clark (e)
- Douglas MacArthur (s)
- George C. Marshall (po)
- John Marshall (j)
- Thurgood Marshall (j)
- Herman Melville (w)
- Gordon Moore (i,b)
- John Muir (e)
- James Naismith (a)
- John von Neumann (i)
- Sandra Day O'Connor (j)
- Robert Oppenheimer (i)
- Linus Pauling (i)
- Edgar Allen Poe (w)
- Sacajawea (e)
- Charles Schulz (v)
- William Shockley (i) *
- Siegel & Schuster (v)
- Henry David Thoreau (w)
- Andy Warhol (v)
- James Watson (i)
- Orson Welles (f)
- Walt Whitman (w)
- Frank Lloyd Wright (v)
* = putz, but...
Our breakdown for the whole 100, by profession (totals exceed 100 because our list is actually slightly over 100, and some have two professions):
p: presidents: 7
s: soldiers: 6
j: jurists/lawyers: 5
t: other politicians/statesmen: 5
l: labor/rights/activists: 7
e: adventurers/explorers/astronauts/pioneers: 13
i: scientists/inventors: 22
v: visual arts/design/architecture: 9
w: writers: 11
f: film/tv: 4
m: musicians: 4
a: athletes: 5
b: business: 5
r: religion: 2
o: other: 2
Eliminate (56):
- Armstrong, Lance
- Armstrong, Neil
- Ball, Lucille
- Bush, Barbara
- Bush, George H. W.
- Bush, George W.
- Bush, Laura
- Carter, Jimmy
- Charles, Ray
- Clinton, Bill
- Clinton, Hillary
- Cosby, Bill
- Cruise, Tom
- DeGeneres, Ellen
- Earhart, Amelia
- Eastwood, Clint
- Edwards, John
- Eisenhower, Dwight (s,pr)
- Favre, Brett
- Gibson, Mel
- Giuliani, Rudolph
- Hanks, Tom
- Hefner, Hugh
- Hepburn, Katharine
- Hope, Bob
- Hughes, Howard
- Jackson, Michael
- Jobs, Steve
- Johnson, Lyndon B.
- Jordan, Michael
- Kennedy, Robert F.
- Kennedy Onassis, Jacqueline
- Limbaugh, Rush
- Lucas, George
- Madonna
- McGraw, Dr. Phil
- Monroe, Marilyn
- Moore, Michael
- Nixon, Richard
- Obama, Barack
- Parks, Rosa
- Powell, Colin
- Reagan, Ronald
- Reeve, Christopher
- Rice, Condoleezza
- Roosevelt, Eleanor
- Sagan, Carl
- Schwarzenegger, Arnold
- Sinatra, Frank
- Spielberg, Steven
- Stewart, Jimmy
- Stewart, Martha
- Tillman, Pat
- Truman, Harry
- Trump, Donald
- Walton, Sam
- Winfrey, Oprah
- Woods, Tiger
Honorable Mentions:
- Isaac Asimov
- Carl Barks
- Vannevar Bush
- John Coltrane
- Charles Curtis
- Miles Davis
- Phillip K. Dick
- Elizabeth Dole
- Duke Ellington (m)
- Philo T. Farnsworth
- William Faulkner
- Geraldine Ferraroo
- Hal Foster
- Hugo Gernsback
- Samuel Gompers
- U.S. Grant
- Devil Anse Hatfield
- Nathaniel Hawthorne
- Robert Heinlein
- Frank Herbert
- Billie Holliday
- Harry Houdini
- Mother Jones
- Bob Kahn
- Bob Kane
- Chief Logan
- Mercury Seven, the rest
- Nancy Landon Kassebaum
- Walt Kelly
- Chief Logan
- Wilma Mankiller
- Winsor McKay
- Charlier Parker
- Frances Perkins
- Jon Postel
- James Randi
- Norman Rockwell
- Nellie Tayloe Ross
- Chief Seattle
- Claude Shannon
- Upton Sinclair
- Dr. Spock
- Jim Thorpe
- Gore Vidal
- Booker T. Washington
- Laura Ingalls Wilder
- Woodrow Wilson
- Woodward & Bernstein
- Daniel Carter Beard & William D. Boyce
Monday, October 03, 2005
Stop the Myth: QKD doesn't fix what Shor broke
[Update: See More on the Myth.]
There is a lot of confusion about the relationship between two of the most famous results in quantum information theory: Shor's algorithm for factoring large numbers on a quantum computer and quantum key distribution (QKD) (developed originally by Charles Bennett and Giles Brassard in 1984). Shor's algorithm, of course, has implications for public-key cryptography.
It's important to note that a) QKD does NOT solve what Shor's factoring algorithm broke, and b) key exchange/distribution is not the biggest security problem we have on the net (it might not even make the top ten). The primary use of public-key cryptosystems is distributed authentication. The primary use of QKD will be key generation/exchange. They serve very different roles in the Internet. A secure Internet communication consists of several distinct parts - authentication of the parties involved, generation of a secure session key, and then the data encryption itself.
Your Internet Explorer, Mozilla, or Firefox comes with Verisign's public key built in. This allows you to check that yes, indeed, Verisign signed the key that says it came from Amazon.com, and therefore you can believe that you are truly connected to Amazon. This is what we call authentication.
After this authentication step, you must create a shared, secret key to continue the communication. That key exchange is often done via Diffie-Hellman key exchange, which allows parts of the communication to be done in the open (unencrypted). D-H by itself is vulnerable to a man-in-the-middle attack, so it is used with some form of authentication to create a shared, authenticated secret key for your session.
The difficulty of cracking a Diffie-Hellman exchange is, I believe, founded on the difficulty of the discrete logarithm problem, and hence is vulnerable to Shor. HOWEVER, D-H is not the only classical method of doing key exchange. If you already have a shared secret, it is easy to negotiate a key without D-H. I used to work for a startup that did IPSEC gateways (though I am FAR FAR from an expert on this), and I believe most of our customers did their authentication via pre-shared secret key. Though the IKE (Internet Key Exchange) built on that secret key authentication does use D-H, that can be fixed (by modifying the RFCs); when you have a pre-shared secret, you can easily use it to encrypt a new key chosen by one of the parties.
So Shor breaks public-key (PK) crypto. What are the implications? Without PK, our key management headaches get worse, but there is (almost?) nothing we can do with public key we can't do with private key. The scalability of authentication servers is problematic and the number of keys you keep around on your systems grows, but in practice probably not nearly as much as people fear, since most people really only connect securely to a few places, anyway.
Okay, so can QKD take over the role filled by PK crypto? After all, the physicists talk about it being impossible to break because of the physics. Nope, and for a simple reason: QKD still requires a classically-authenticated channel; that is, it still requires the functionality that Shor broke! It doesn't fix Shor. But, if you have authentication you can trust today, regardless of whether it is PK or not, you're set; the authentication information is not used in the generation of the key used to encrypt the data.
I sat in on a talk on QKD by Todd Brun at ISI's div7, in front of thirty or forty of the planet's best networking researchers. They immediately started jumping up and down and stamping their feet about man-in-the-middle attacks and the need for the authenticated channel. Todd remarked something to the effect that the physicists, if they are aware of the problem at all, are much less cognizant of its operational implications. Paterson et al. wrote a nice paper on the implications of QKD, where much of what I've written here is discussed, and probably more coherently.
QKD's place is for the truly, truly paranoid: people who believe that their traffic is being snooped today, and that classical, symmetric crypto (3DES, AES) will fall to either mathematical advances or some further quantum computing advance sometime in the distant future, and don't want their traffic from TODAY read by somebody half a century from now. Authentication that is good enough TODAY, plus QKD, is good enough to guarantee that your data is safe for all time (modulo breakins/breakdowns at the end points).
In that case, your only operational choice is to use the QKD-generated key as a one-time pad, and discard; if you're really paranoid enough to want the QKD, don't use it to just generate keys for use with a symmetric crypto protocol. That means you need very high QKD bit-generation rates, and most are still in the kilobits/second. Some experiments have been done in the low megabits/sec., but that's pre-filtering, I believe, which costs you at least one order of magnitude in performance. I was at a talk by Tomita-san, one of NEC's QKD experts, just a couple of days ago, and he was talking about an experimental setup over 16km of real-world fiber on telephone poles that did QKD at an average rate of 13 kilobits/second. The most advanced engineering demonstration is the BBN/Harvard/Boston U. network, see some of Chip Elliott's papers.
I arrived at the party a little late to get in on the recent thread at Dave Bacon's Quantum Pontiff blog, but I did throw in my two cents anyway, see the comments here. There was also some discussion on Dave Farber's IP list, see here and search for quantum or Armstrong.
There is a lot of confusion about the relationship between two of the most famous results in quantum information theory: Shor's algorithm for factoring large numbers on a quantum computer and quantum key distribution (QKD) (developed originally by Charles Bennett and Giles Brassard in 1984). Shor's algorithm, of course, has implications for public-key cryptography.
It's important to note that a) QKD does NOT solve what Shor's factoring algorithm broke, and b) key exchange/distribution is not the biggest security problem we have on the net (it might not even make the top ten). The primary use of public-key cryptosystems is distributed authentication. The primary use of QKD will be key generation/exchange. They serve very different roles in the Internet. A secure Internet communication consists of several distinct parts - authentication of the parties involved, generation of a secure session key, and then the data encryption itself.
Your Internet Explorer, Mozilla, or Firefox comes with Verisign's public key built in. This allows you to check that yes, indeed, Verisign signed the key that says it came from Amazon.com, and therefore you can believe that you are truly connected to Amazon. This is what we call authentication.
After this authentication step, you must create a shared, secret key to continue the communication. That key exchange is often done via Diffie-Hellman key exchange, which allows parts of the communication to be done in the open (unencrypted). D-H by itself is vulnerable to a man-in-the-middle attack, so it is used with some form of authentication to create a shared, authenticated secret key for your session.
The difficulty of cracking a Diffie-Hellman exchange is, I believe, founded on the difficulty of the discrete logarithm problem, and hence is vulnerable to Shor. HOWEVER, D-H is not the only classical method of doing key exchange. If you already have a shared secret, it is easy to negotiate a key without D-H. I used to work for a startup that did IPSEC gateways (though I am FAR FAR from an expert on this), and I believe most of our customers did their authentication via pre-shared secret key. Though the IKE (Internet Key Exchange) built on that secret key authentication does use D-H, that can be fixed (by modifying the RFCs); when you have a pre-shared secret, you can easily use it to encrypt a new key chosen by one of the parties.
So Shor breaks public-key (PK) crypto. What are the implications? Without PK, our key management headaches get worse, but there is (almost?) nothing we can do with public key we can't do with private key. The scalability of authentication servers is problematic and the number of keys you keep around on your systems grows, but in practice probably not nearly as much as people fear, since most people really only connect securely to a few places, anyway.
Okay, so can QKD take over the role filled by PK crypto? After all, the physicists talk about it being impossible to break because of the physics. Nope, and for a simple reason: QKD still requires a classically-authenticated channel; that is, it still requires the functionality that Shor broke! It doesn't fix Shor. But, if you have authentication you can trust today, regardless of whether it is PK or not, you're set; the authentication information is not used in the generation of the key used to encrypt the data.
I sat in on a talk on QKD by Todd Brun at ISI's div7, in front of thirty or forty of the planet's best networking researchers. They immediately started jumping up and down and stamping their feet about man-in-the-middle attacks and the need for the authenticated channel. Todd remarked something to the effect that the physicists, if they are aware of the problem at all, are much less cognizant of its operational implications. Paterson et al. wrote a nice paper on the implications of QKD, where much of what I've written here is discussed, and probably more coherently.
QKD's place is for the truly, truly paranoid: people who believe that their traffic is being snooped today, and that classical, symmetric crypto (3DES, AES) will fall to either mathematical advances or some further quantum computing advance sometime in the distant future, and don't want their traffic from TODAY read by somebody half a century from now. Authentication that is good enough TODAY, plus QKD, is good enough to guarantee that your data is safe for all time (modulo breakins/breakdowns at the end points).
In that case, your only operational choice is to use the QKD-generated key as a one-time pad, and discard; if you're really paranoid enough to want the QKD, don't use it to just generate keys for use with a symmetric crypto protocol. That means you need very high QKD bit-generation rates, and most are still in the kilobits/second. Some experiments have been done in the low megabits/sec., but that's pre-filtering, I believe, which costs you at least one order of magnitude in performance. I was at a talk by Tomita-san, one of NEC's QKD experts, just a couple of days ago, and he was talking about an experimental setup over 16km of real-world fiber on telephone poles that did QKD at an average rate of 13 kilobits/second. The most advanced engineering demonstration is the BBN/Harvard/Boston U. network, see some of Chip Elliott's papers.
I arrived at the party a little late to get in on the recent thread at Dave Bacon's Quantum Pontiff blog, but I did throw in my two cents anyway, see the comments here. There was also some discussion on Dave Farber's IP list, see here and search for quantum or Armstrong.