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The recent “How Quantum is the D-Wave Machine?” Shin et.al. paper (dwave.wordpress.com)
39 points by jonbaer on Feb 4, 2014 | hide | past | web | favorite | 32 comments

Impressive. This guy goes to the extent of linking to the transcript of a talk perfectly irrelevant to the point. But he cannot link to the paper he is criticizing.

So here it is:

Shin et al. How "Quantum" is the D-Wave Machine? http://arxiv.org/abs/1401.7087

Scott Aaronson is one of the main D-Wave skeptics. His most recent post on the subject has a nice overview on the latest works on d-wave "quantumness":


He starts with his philosophy of what science is, which is apparently based on a TED talk by David Deutsch:

"...good explanations for why things are the way they are."

Oh no. Science, emphatically, does not answer why, or at least not the ultimate why. It answers how; it provides a set of models.

To quote Feynman, "While I am describing to you how Nature works, you won't understand why Nature works that way. But you see, nobody understands that." from QED: The Strange Theory of Light and Matter, p. 10.

You're interpreting "explanations" in a different way than he meant it.

You're looking for philosophical or religious explanations, but scientific theories by their nature apply to more than one instance, and therefore explain, from one instance to the next, why things continue to behave in similar ways.

If the many-worlds theory is correct and things are the way they are because this happens to be the one universe where they're that way, that wouldn't satisfy you because you'd want to know why universes exist at all, why the quantum fluctuations exist that lead to the big bang.

If a grand unifying theory existed that provided a tautology proving that it, and only it, could ever be the underlying theory behind physics, you'd want to know why. Why is there physics at all?

There are no underlying explanations of that kind. Even if you believe in God, why he chose one form of physics laws rather than another can never be explained unless someone has the good fortune to be in contact and write it down in a holy book, and someone will still ask why God made that choice and not another, or why that God exists and not another; any tautological argument for God can apply to a universal theory explaining all of physics: "it is because it is". Philosophy can only offer insights about how to think about human existence in a helpful (sociologically and psychologically helpful) way, but has nothing to say about the origins of physical theories.

> Why is there physics at all? There are no underlying explanations of that kind.

But that use of "why" is not an explanation, it's a justification or rationalization. I may say that the Big Bang explains the present universe, but that explains "how", it doesn't address "why".

> ... scientific theories by their nature apply to more than one instance, and therefore explain, from one instance to the next, why things continue to behave in similar ways.

No, not "why," but "how". For example, natural selection is an explanation, a mechanism, a "how". Not a justification, a reason, a "why".

Obviously in common usage, "why" and "how" may be seen as interchangeable, so this becomes a tempest in a teapot.

It's just semantics.

> It's just semantics.

Yes, it's semantics, but I would hesitate to say "just semantics".

I agree that It does not answer why in general, but that quote in particular seems reasonable -- Deutsch is referring to the whys which result from more fundamental interactions (more fundamental models); although eventually, you reach the basic laws of science and then there's really no point in further asking why.

Thanks for making this important point. Science explains, it doesn't justify or rationalize. And each of science's explanations is open to falsification by new evidence.

Actually, "how" is "why".

> Actually, "how" is "why".

In a scientific context, "how" and "why" are generally regarded as separate questions. Consider the classic case of peppered moth evolution: the "how" is answered by natural selection -- through random genetic variations the moths changed color over time to match their changing environment. The "why" is answered by noting that the camouflaged moths escaped predation by moth-eating species.

Speaking as a relatively qualified epistemologist, I nod.

Your philosophy is a couple thousand years stale. https://en.wikipedia.org/wiki/Four_causes

When I read this blog post, it was like opening a Christmas present and getting socks.

I don't know much about the state of the art, the points in contention between the people in this argument, or quantum computing in general. An article that explained the competing standards for what constitutes a quantum computer and either made a case for why one standard is more useful or described how one participant's argument was inconsistent with their standard would have been genuinely helpful. Instead I read a link to a TED talk, epistemological meta-babble, and a promise that further experiments are incoming.

This company may be completely legitimate and its product may be the most revolutionary thing since sliced bread, but I didn't know before I read this post, I don't know now, and I now think their CTO sounds too Steorn-y for comfort.

Wasn't one of the major points about the D-Wave machine that while it appeared to work quantum like with low numbers of qubits, it appeared classical once you actually started doing real work?

This would perfectly align with the defended studies. Additionally it would also align with what skeptics claim it is doing, performing some efficient classical analysis on custom hardware.

Unfortunately the meat is missing from this response, specifically a non-trivial example of definitely quantum data.

>> chief technology officer of D-Wave and 2010 NAGA Brazilian jiu-jitsu light heavyweight world champion.

He could always challenge skeptics in a fight to the death.

Which is why clever skeptics should insist on pistols at 20 paces.

Hey, it worked for Uwe Boll.

I recently had the pleasure of talking about this particular subject over beers with someone very close to the quantum computing community.

The short answer is: "They aren't really doing quantum computing. They're essentially cheating."

But, I'm no quantum mechanic PhD, so it's not first hand knowledge as to why.

It seems quite likely that whoever turns quantum computing into something practical will face exactly that criticism from the academic quantum computing community, largely since it appears construction of what they think of as proper quantum computers doesn't seem to be too feasible. If D-Wave have managed it I must admit I'd be surprised, but the amount of venom thrown their way is curious.

The venom is understandable in any competition (and the battle to build a working, useful quantum computer is a major competition between both companies and universities) where just about every knowledgeable person is convinced someone cheated.

I think the jury will remain out on this one for the next few generations of D-wave computers. If by the time it reaches 2k-4k qubits, they still can't prove without a doubt that it's at least a special form of quantum computing, then I guess then we'll have our final answer.

From what we've seen (on the nasa/google installation) we're seeing quantum operation, but yes, once we see 2k qubit chips (which we hope happens within the year) that's when we'll know about whether there is an actual advantage vs scalar processors for annealing problems.

This is one of the reasons we're all going round and round on proving 'quantumness' so that when we get a processor with more qubits we can predict and test that it is indeed all that an a bag of chips.

how do you know you are seeing quantum operation?

"D-Wave's Dream Machine" is a good article I submitted recently that never made the front page.


"When I saw how trivially wrong it was it was like opening a Christmas present and getting socks."

Wait, what is wrong with getting socks at Christmas? >_>

He can't use his ju-jitsu while wearing socks!

> D-Wave answers "How Quantum is the D-Wave Machine?"

This is the first time I've heard "quantum" used as an adjective. But probably not the last.

How quantum? Very quantum. Such entanglement. Wow.

Isn't the 'quantum' in "quantum mechanics" an adjective?

> Isn't the 'quantum' in "quantum mechanics" an adjective?

Is "mathematical" in "mathematical physics" an adjective or a noun? I think it's a noun. On the other hand, the "extreme" in "extreme physics" is an adjective.

Now for a gray-area example. If I say "very mathematical physics", then "mathematical" becomes an adjective.

And I might be wrong about this. :)

> I think it's a noun.

On what grounds? It's being used to modify a noun ("physics"), and can be modified by an adverb ("very"). This is characteristic of an adjective.

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