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D-Wave Quantum Computing Solution Raises More Questions 143

Posted by Soulskill
from the may-or-may-not-be-D-wave-of-the-future dept.
benonemusic writes "The commercially available D-Wave computer has demonstrated its ability to perform increasingly complex tasks. But is it a real quantum computer? A new round of research continues the debate over how much its calculations owe to exotic quantum-physics phenomena. 'One side argues there is too much noise in the D-Wave system, which prevents consistent entanglement. But in an adiabatic device, certain types of entanglement are not as vital as they are in the traditional model of a quantum computer. Some researchers are attempting to solve this conundrum by proving the presence or absence of entanglement. If they show entanglement is absent, that would be the end of the discussion. On the other hand, even if some of D-Wave's qubits are entangled, this doesn't mean the device is taking advantage of it. Another way to prove D-Wave's quantumness would be to confirm it is indeed performing quantum, and not classical, annealing. Lidar has published work to this effect, but that triggered opposition, and then a counter-point. The debate continues.'"
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D-Wave Quantum Computing Solution Raises More Questions

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  • by aleator (869538) on Saturday October 19, 2013 @07:16PM (#45177939) Homepage
    how do you show the presence of entanglement without disturbing it?
    • by Frosty Piss (770223) * on Saturday October 19, 2013 @07:45PM (#45178069)

      how do you show the presence of entanglement without disturbing it?

      You ask Schrodinger's cat. He has the answer...

    • how do you show the presence of entanglement without disturbing it?

      Analyze it with a quantum computer.

    • by Roger W Moore (538166) on Saturday October 19, 2013 @11:12PM (#45178859) Journal
      Measure correlations between the two systems. If you have entangled, oppositely polarized photons and you simultaneously pass them through aligned polarizers then one will always pass through the filter and one will always fail. It is impossible to recreate this in any classical system without communication between the photons.

      If you can perform the same type of measurement with entangled qbits in a manner where it is physically impossible for them to communicate (e.g. make the two measurements simultaneously) you can confirm their quantum nature.
    • by edelbrp (62429) on Sunday October 20, 2013 @01:50AM (#45179251)

      You can do what Alain Aspect did which was to show that statistically a system can show the repeatable statistical measurements (using Bell's Theorem) that indicate that entanglement is happening. Then let the system/computer do it's thing with some confidence that entanglement is in play.

    • by drolli (522659) on Sunday October 20, 2013 @04:54AM (#45179577) Journal

      Experimentally entanglement is shown most strongly in the form of Bell violations:

      http://en.wikipedia.org/wiki/Bell's_theorem [wikipedia.org]

      as e.g.

      http://www.nature.com/nature/journal/v461/n7263/abs/nature08363.html [nature.com]

      did.

    • Simple. Make it do something only a quantumly entangled system could do in a given time period like reverse factorization or whatever. So far, they haven't done that. Their excuse is a lack of sufficient quantities of qubits to determine a speed change in factorization. Basically a normal CPU or ASIC could have solved the equation they demonstrated in 1 ms but a quantum one could solve it in a billionth of a millisecond but you can't measure that small of a time frame so you have to take their word on i
  • We have Google. [slashdot.org]
  • by Impy the Impiuos Imp (442658) on Saturday October 19, 2013 @07:36PM (#45178033) Journal

    Can someone explain to me how this chip could be calculating anything unless the quantum part was working?

    Isn't it like a car that has an electric motor or a gas one, but not both? How can they be confused which engine is running? Who builds a backup normal processor then what, it fills in if the quantum one doesn't work right, and they have no way to tell if this backup kicked in?

    • by InfiniteLoopCounter (1355173) on Saturday October 19, 2013 @07:54PM (#45178105)

      Can someone explain to me how this chip could be calculating anything unless the quantum part was working?

      D-wave is very secretive about how their machine operates and do not respond to academics who want to know exactly how it works -- this is the source of much of the speculation. On top of that you need to specially code your instructions for it, because it can only do a subset of what a general quantum computer could in theory do.

    • by HuguesT (84078) on Saturday October 19, 2013 @07:58PM (#45178127)

      The D-Wave engine can indeed solve some specific optimisation problems by a method called adiabatic annealing. Essentially this done by encoding the problem to be solved in some initial state of the physical components of the engine, and letting it evolve without exchanging energy with the outside world (this is what adiabatic means). The evolution is done in such a way that the solution to the optimisation problem eventually appears (this is the annealing part) with some probability.

      The engine definitely works, this is not disputed. However there is some debate whether the way the engine works is essentially classical or essentially quantum. At the moment the engine is not especially powerful and it is very noisy, so there is no easy way to tell. In the 3 papers cited in the Fine Article, one says this is definitely quantum because the way the system evolves does not match the way classical annealing is simulated (simulated annealing (SA) is a very popular way to solve some complex classical optimisation problems). The second paper says that it is still possible to achieve the signature observed in the first paper by purely classical means, so this is not so clear. The third papers says that this is correct, but that there is more to the signature than was reported in the first paper, and that *this* is more likely to be quantum than not.

      Feel free to contradict me. At any rate, and this is not disputed, the D-Wave engine does not work in the way quantum computers are expected to work in the literature about this topic. It would not be useful to solve factorisation problems as in the Shor algorithm [wikipedia.org]. Rather, it would be useful to solve some optimisation problems in a faster way than with classical or traditional CPUs or GPU. This is still very useful, although at the moment the D-Wave computer's inner working are mostly secret, not hugely fast, and noisy. So D-Wave's qbits are a bit of a misnomer. They should be called something different so as not to engender confusion, perhaps obits (optimisation bits)?

      I hope this make sense to you.

      • Re: (Score:3, Insightful)

        by Garridan (597129)
        Yeah... I watched a talk by a D-Wave guy. This is a summary of his talk: "So, you have an NP-Complete problem. We have a quantum solver that works on a large graph with a special structure. If you can find a homomorphism from your problem into our graph structure, and you can figure out how slowly to evolve the adiabatic process, then we can solve your problem!"

        Okay, that's great. But finding that graph homomorphism? Probably NP-Complete itself. Figuring out how slowly to evolve the system? I have
        • by HuguesT (84078) on Sunday October 20, 2013 @06:23AM (#45179781)

          Theoretical Quantum computer using entanglement to perform their calculations make no claim to solve NP-hard problems. They can only solve some very specific class of problems, that are well identified but are still interesting. Integer factorisation is one of them, but factorisation is not thought to be in NP-complete [wikipedia.org], although we are not certain at this stage.

          There is an old article in PNAS that says that adiabatic quantum computers are theoretically no better [pnas.org] than classical computers at solving NP-hard problems. So even if D-Wave had a truly working adiabatic quantum computer, it is not clear that it would perform orders of magnitudes better than what we have now.

          Anyway all of this is very interesting to watch, but the fact that D-Wave is so secretive is not very compatible with progress in the field.

    • by gweihir (88907)

      Ordinarily, you would look at the computing power. If it is significantly larger than conventional physics can explain, it must use quantum effects. Unfortunately, this "magic black box" is in no way faster than traditional computers, just a lot more expensive, hence the hand-weaving.

      My money is on this being pure fraud. Would not even surprise me if there is a conventional computer hidden in there somewhere that does the calculations.

      • by HuguesT (84078)

        I'm personally reasonably convinced that D-Wave's engine is novel and does offer some new ways of performing various specific calculations. The literature about it exists and is quite interesting for people interested in optimisation. However I'm not sold to the technology yet, essentially classical CPUs can perform the same type of calculation that D-Wave's computer can at the moment, at a much lower cost. This might change in the future though.

      • by quax (19371) on Saturday October 19, 2013 @11:36PM (#45178921)

        I recently visited D-Wave looked at their chips and deep freeze containment. Shot a snapshot of Geordie Rose standing in one of the open boxes. [wavewatching.net]

        You may think they are misguided, but their tech is for real. Even Scott Aaronson doesn't deny that.

        There is no classical computer hidden inside, but there is still reasonable doubt as to exactly how quantum the device is, and if it will ever deliver clear cut quantum speed-up.

        • by fatphil (181876)
          Whoever wrote that article has absolutely no interest in communicating clearly.

          When such people are supportive of D-Wave, it adds no credibility to D-Wave at all. If anything, it reinforces the prejudices that many have against them.

          So, they've left "stealth" mode, and are now in full-on "buzzword bingo" mode?
        • by gweihir (88907)

          You do realize that you can put classical computers on deep-frozen chips, do you? And that they tend to run _very_ fast in that situation?

          • by quax (19371)

            That'll be a lot of effort for a fraud, especially since you then have to fake all the qubit specific data that goes into the publications. And the chip samples they have on display very much looks like Josephson junctions circuits and nothing like regular chips. (And the integration density they have for this process could not at all deliver reasonable classical performance).

            • by gweihir (88907)

              And do you realize that Josephson circuits are especially fast and well understood, if not cost-effective? And that in addition there does not need to be any resemblance between what they display publicly and what is actually in the machine? And that what is actually in the machine does not need to be created with the same process or by them at all? Until somebody competent in detection technological fraud disassembles one of these, we do not know. I bet disassembly voids the warranty or even destroys the t

              • by quax (19371)

                I've been following the Rossi story as well and agree that it is a fraud, but the comparisons to the ecat are only superficial. [wavewatching.net]

                The contraptions Rossi builds are cheap and look like a plumber put them together. On the other hand D-Wave has chips samples on display that are produced by a special purpose foundry that can produce Niobium SC circuitry. That took some serious investments.

                Rossi supposedly sold his house to finance his venture, D-Wave is backed by the likes of Steve Jurvetson and Jeff Bezos. Ross

  • Hasn't the benchmarks already placed it above pretty much any computer in the tasks it can do within its full size?

    Mind you, I guess even if that were true, if it wasn't quantum entanglement taking place, it would still be pretty big because they still managed to find a way to make a non-quantum computer way ahead of the competition.

    If it is a quantum processor, it would be similar to say... the math co-processor, still baby steps towards a full, integrated circuit.
    They even say themselves that it is only u

    • by gweihir (88907)

      Last state of my knowledge is it is slower than a traditional computer in a fair comparison. There are some benchmarks though that have a traditional computer simulate this thing, and, not surprisingly, the simulation is slower than the real thing. That is about the most unfair comparison possible though.

    • by the gnat (153162) on Saturday October 19, 2013 @09:09PM (#45178411)

      Hasn't the benchmarks already placed it above pretty much any computer in the tasks it can do within its full size?

      My understanding was that the benchmarks - at least the one that was quoted as showing a "3600x speedup" - weren't even comparing the same thing: the D-Wave computer was running the quantum adiabatic annealing method, which is the only way it can be programmed, while the conventional CPU was running an exact solver. The latter is expected to be vastly less efficient (but more precise). When a group of computer scientists came up with an annealing method to solve the same problem on a conventional CPU, they ended up with something just as fast as the D-Wave system.

      • by quax (19371) on Saturday October 19, 2013 @11:24PM (#45178895)

        The benchmark did indeed not demonstrate a quantum speed-up, but it in fairness to D-Wave this was a test designed based on the customers requirements i.e. for them acing this benchmark was good enough to justify investing in this technology.

        My understanding is that the algorithm that was comparatively fast on a classical computer was hand optimized by a graduate student, it was not a generic annealing algorithm solver.

        But the paper on this effort of 'beating' D-Wave on a classical machine is yet to be published, so this is all from blog hearsay.

        • by amaurea (2900163) on Sunday October 20, 2013 @05:13AM (#45179603) Homepage

          Could you elaborate a bit on this? I had the impression that D-Wave's users had to map their problem to fit what D-Wave computes, not the other way around. That would make comparisons with a specialized software solver appropriate, wouldn't it?

          The blog post in question [archduke.org] also includes a link to the source code [github.com] of the specialized solver (Prog-QAP), and others have confirmed that it produces the same results as CPLEX, the general solver that D-Wave beat.

          CPLEX is indeed slower than D-Wave, though newer versions have brought the factor down from 3600x to 14x [ibm.com]. But again, CPLEX is a general solver, while D-wave is specialized hardware. The specialized software solver Prog-QAP is *much* faster than CPLEX, and gets a 12000x speedup over D-Wave when running on a single core.

          But all of that is a bit old, and it may be that D-Wave has produced more impressive results after that. I hope D-Wave's approach results in something able to beat classical computers, even if it doesn't lead to a general quantum computer. But I really dislike all the secrecy they employed - that is not how science is supposed to work. The fraud speculations they have had to endure are entierly self-inflicted due to this secrecy.

          • by quax (19371)

            I was referring to the paper by Mathias Troyer et. al. that is yet to be published not the effort that Alex Selby writes about (thanks for the link).

            Will have to read the latter in more detail to get a good grasp of how much effort is required to beat the benchmark with Alex's approach. Two caveats: On first glance I am not sure if he has the same training data (he mentions he communicated with Cathy McGeoch) - if he does it'll be interesting to see how stable his generic approach is when the problem domai

  • I doubt it. It is however far more expensive and is making its "inventors" a tidy profit at zero benefit to those stupid enough to buy one.

  • the 'race' to quantum computing is all about Marketing: "Now with QUANTUM technology!"

    everyone wants to be the computing/physics genius who 'ushers humanity into a new era of computing'....someone might mention the 'singularity'

    properly understood, Quantum Entanglement is at the core of all Quantum Physics [wikipedia.org]

    if a research group **truly** were able to maintain a standing quantum entangled state with **non-local force transfer** and **quantum teleportation of information** [wikipedia.org] then that would be, essentially, the

    • properly understood, Quantum Entanglement is at the core of all Quantum Physics [wikipedia.org]

      No it is not. It is one of the features of quantum physics which is the hardest to understand and, arguably, we still do not have a good grip on it. However that by no means puts it at the core of all quantum physics: there is far more to QM than quantum entanglement e.g. tunnelling, self interference etc.

  • Just do it. (Score:5, Interesting)

    by CanEHdian (1098955) on Saturday October 19, 2013 @08:45PM (#45178287)
    There should be plenty of problems a quantum computer could solve in polynomial time that would take classic computers eons to solve. Start solving those problems and it's a quantum computer. Simple as that.
    • Re: (Score:3, Informative)

      by edelbrp (62429)

      They have. We're still waiting for the classical computers to finish to compare answers. Should just take a few eons. Then we'll know it works.

    • by AmiMoJo (196126) *

      Exactly, it doesn't really matter if it is a real quantum computer or not, only that it can complete certain computations that people need much faster than a traditional computer. If it solves that problem for someone then the rest of the debate is academic.

      • Exactly, it doesn't really matter if it is a real quantum computer or not, only that it can complete certain computations that people need much faster than a traditional computer. If it solves that problem for someone then the rest of the debate is academic.

        Wait, it does matter whether this is a quantum computer or not. If it *is* a quantum computer then the calculations can be trusted to be accurate and precise based on the fundemental principles driving the solutions. If it is *not* a quantum computer all the results from the machine may be so horribly wrong that they cause serious accidents, damage or loss of life. The problem as stated above in the comments is that some of the calculations take so egregiously long ("eons") on traditional computation devic

        • by AmiMoJo (196126) *

          That's not how quantum computers work or how they are used. You don't get a definite answer, just a highly probable one. You then have to verify it with a normal computer. The problem that the quantum computer solves is that a normal computer has to try every verifying possible answer until it finds the right one. Each test may only take fractions of a second, but you have to do so many of them it takes an unreasonable amount of time.

  • by Required Snark (1702878) on Saturday October 19, 2013 @08:52PM (#45178343)
    Consider the hypothesis that the DWave machine is a superposition of classical and quantum computing. By some observations it is classical, by others quantum. As some point a measurement will be preformed on the machine, and it's state will resolve into either a classical physics computing device or a quantum physics computing device.

    This situation is completely reasonable give the current state of the art in quantum computing.

    Making accusations of "marketing hype" and unethical behavior are irrelevant. Whatever it's doing, it's not digital computing. Even if it turns out to be classical physics, it is still advancing the state of the art in non-digital computing.

    No matter how DWave does in the future, quantum computing is still going to happen in the near term. Dwave is not going to change that under any circumstances.

    Getting bent out of shape over this is a waste of effort. Even the experts are not in agreement. This is how progress occurs at the cutting edge.

  • In the longterm of things, all proprietory systems will be just noise

  • No way I'm gonna try one of these until they get the bugs out. Instead of a blue screen, I'll get a black hole and those Higgs bosons all over the carpet. My wife will kill me. Plus, they probably cost like over a thousand bucks.

    But I bet GTA V runs like a banshee on it. No screen tearing, but possibly tearing in the fabric of space and time. As soon as Tiger Direct starts selling them, I'm in for one, but you best believe I'm gonna be wearing my lead codpiece when I sit in front of that thing.

  • by Dialecticus (1433989) on Saturday October 19, 2013 @10:58PM (#45178819)
    Answer: It's *SO* quantum that even the issue of whether or not it's quantum exists in a superposition of states!
  • by quax (19371) on Saturday October 19, 2013 @11:13PM (#45178861)

    ... I got the impression that he is not overtly concerned about this ongoing controversy [wavewatching.net], although he did mention he prepared another paper to demonstrate entanglement on the chip.

    But his focus is clearly on tackling hard tasks with immediate applicability (for instance in deep learning).

     

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