Some Scientists Question Whether Quantum Computer Really Is Quantum 170
gbrumfiel writes "Last week, Google and NASA announced a partnership to buy a new quantum computer from Canadian firm D-Wave Systems. But NPR news reports that many scientists are still questioning whether new machine really is quantum. Long-time critic and computer scientist Scott Aaronson has a long post detailing the current state of affairs. At issue is whether the 512 quantum bits at the processor's core are 'entangled' together. Measuring that entanglement directly destroys it, so D-Wave has had a hard time convincing skeptics. As with all things quantum mechanical, the devil is in the details. Still it may not matter: D-Wave's machine appears to be far faster at solving certain kinds of problems (PDF), regardless of how it works."
If it works - it works (Score:2, Insightful)
Does it really matter so long as it does what it says on the tin? It works faster, surely that's all that matters?
Re:D-Wave's Dirty Little Secret (Score:5, Insightful)
Entanglement isn't the only issue (Score:5, Insightful)
Scott's blog post and the comment thread there are really worth reading. Entanglement isn't the only issue. A major part of this also is whether the process that the D-Wave machine is doing is anything that is even faster (either in practice or asymptotically) than a classical computer. Right now, the answer for the first is clearly no. Scott describes mildly optimized systems which have been shown to effectively outperform D-Wave at its own problem. The second question- of asymptotic performance is a little trickier but the answer looks like "probably not". It is also worth noting that the D-Wave machines do a very specific optimization problem, of unclear usefulness, and cannot be used at all for many of things that we think of as what one wants a quantum computer for, like Shor's algorithm http://en.wikipedia.org/wiki/Shor's_algorithm [wikipedia.org] to factor integers.
In fairness to D-Wave though if one thinks of this as essentially a research machine, then not doing as well as conventional systems isn't that much of mark against it any more than very early cars being slower than horses. However, D-Wave is trying to sell these machines commercially. And Scott expresses worry that there's going to be a serious backlash against quantum computing as a whole when the the D-Wave hype bubble bursts. Apparently, D-Wave has now gotten about 100 million in funding, so at least, this is an extremely suboptimal allocation to resources when much more promising academic quantum computer research projects are getting much less money.
Re: Read the blog post (Score:4, Insightful)
But what if I build a standard internal combustion engine, wrap it in a sheet of tin foil, and proclaim that I have created a portable cold fusion generator? Is that worth $10m for advancing cold fusion technology, despite the fact that it's not actually cold fusion?
The issue with D-Wave isn't that it's not as good as classical methods, it's that it probably isn't what it claims to be.
Re:D-Wave's Dirty Little Secret (Score:2, Insightful)
" If one adjusts one's perspective to think of quantum mechanics more as the consequences of using a 2-norm and looking then at the structure imposed on vectors by unitary transformations, things make a lot more sense."
Which means absolutely nothing to the vast majority of people; hence spooky, magical and hard to understand.