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...