Quantum computers: they’re not just for breaking RSA

People with cryptography obsessions or who only pay attention to casual news may think quantum computers are only useful for breaking cryptosystems like RSA.  In fact, they should also prove quite useful for a number of physical chemistry problems.  A new paper just out analyzes its use in classical Bayesian networks.  I haven’t read through the whole thing yet, but it seems like a pretty interesting application.  What I’m looking for is something that D-Wave can use that unequivocally proves one way or the other whether or not they have really succeeded in building a quantum computer.

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6 Responses to “Quantum computers: they’re not just for breaking RSA”

  1. If they could accept quantum input then you could use either arXiv:0807.4154 (to big up my own paper) or arXiv:0810.5375 to prove that they have a quantum computer. Unfortunately they don’t have a means to accept qubit inputs. Gah!

  2. quantummoxie Says:

    Hmmm. I wonder if we could devise a test that could be conclusively used to determine whether they’ve really got a quantum computer or not. Since they can’t accept qubits as inputs, we’d have to think of something different, but it would be an intriguing project.

  3. Actually, I think it is provably impossible to do that without quantum communication until the number of qubits is high enough (and noise low enough) that you can no longer simulate the system classically.

  4. quantummoxie Says:

    Well, here’s my idea. Since that is a known limitation, instead hunt for something that would take the fastest classical computer a very long, but finite amount of time to calculate and compare speeds. There must be some way to determine speed up with mid-range problems, as opposed to waiting for them to try to crack something like RSA.

  5. Ian, Thanks for mentioning my paper. D-wave might try some version of quantum simulated annealing. Personally, I think D-wave is a f*cked company. After spending $40M plus over ten years, it still has no commercial product.

  6. quantummoxie Says:

    Yeah, I think the long-term viability of D-Wave is certainly questionable unless they put together something commercially viable soon. Having been a small business owner once, I was in the position of trying to do just that – and I failed, hence I am now an academic.

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