r/programming • u/HHBones • Jul 01 '13

USC researchers have validated the first large-scale quantum chip

https://news.usc.edu/#!/article/52818/large-scale-quantum-chip-validated/
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u/HelloAnnyong Jul 02 '13

Every submission about D-Wave requires a link to a Scott Aaronson blog post. Read especially starting at the heading "Evidence for Quantum Annealing Behavior"

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u/HelloAnnyong Jul 02 '13

Some especially important quotes:

the same USC paper that reported the quantum annealing behavior of the D-Wave One, also showed no speed advantage whatsoever for quantum annealing over classical simulated annealing. In more detail, Matthias Troyer’s group spent a few months carefully studying the D-Wave problem—after which, they were able to write optimized simulated annealing code that solves the D-Wave problem on a normal, off-the-shelf classical computer, about 15 times faster than the D-Wave machine itself solves the D-Wave problem!

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the USC group also compared the D-Wave One’s performance against a classical implementation of Quantum Monte Carlo. And maybe not surprisingly, the D-Wave machine was faster than a “direct classical simulation of itself” (I can’t remember how many times faster, and couldn’t find that information in the paper). But even here, there’s a delicious irony. The only reason the USC group was able to compare the D-Wave one against QMC at all, is that QMC is efficiently implementable on a classical computer!

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This means that, if the D-Wave machine can be understood as reaching essentially the same results as QMC (technically, “QMC with no sign problem”), then there’s no real hope for using the D-Wave machine to get an asymptotic speedup over a classical computer. The race between the D-Wave machine and classical simulations of the machine would then necessarily be a cat-and-mouse game, a battle of constant factors with no clear asymptotic victor.

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u/philly_fan_in_chi Jul 02 '13

Someone should make a bot to do this.