5 ms·

Performance of quantum computer no better than ordinary PC, say analysts

46 points by aasarava 12y ago

mpthrapp 12y ago
The title is slightly misleading. This article is only talking about the performance of one specific quantum computer. (The D-Wave Two).
- VonGuard 12y ago
  Are there others that you can buy? As far as I know, D-Wave is the only one out of the lab. I'm totally a D-Wave skeptic, but I do have to state that the scientists who tested this thing sound like idiots, unless they really did try quantum annealing. If the D-Wave guys say they tried the wrong set of equations for the device, I'm inclined to believe them. Even though I don't even believe this thing is really a quantum computer, there are much more specific and defined ways to poke holes in D-Wave than just by running some tests and comparing speed. D-Wave has, very specifically, targeted this machine at one function: http://en.wikipedia.org/wiki/Quantum_annealing http://en.wikipedia.org/wiki/Quantum_annealing Unless you're doing quantum annealing on the D-Wave, it might as well be a toaster, an Android phone, or a Windows PC. It's made to do only quantum annealing. Did D-Wave 2 somehow expand its capabilities? I'm basing this on D-Wave 1 knowledge, but I cannot imagine anything really changed except the number of Qbits inside the thing. All this having been said, the D-Wave has yet to prove that it is even doing Quantum Annealing, let alone that it's faster than a traditional computer at this problem set. No one has shown it to be faster than traditional outside of D-Wave.
  - mpthrapp 12y ago
    I'm not as up on Quantum Computing as I'd like to be, but the title seems to imply that QC as a concept is no faster than regular computing. Which may be true for general purpose computing, but that's never what QC was intended for.
  - shoyer 12y ago
    Yes, of course they did what D-wave calls quantum annealing. As you say, that's all the D-Wave machines can do. The D-Wave executive's claim that the problems used in the study are "not at all the right choice for probing a quantum speedup" is in reference to the specific subtypes of quantum annealing problems that this study looked at, not whether they were doing quantum annealing at all.
Xcelerate 12y ago
The title of the article "Performance of quantum computer no better than ordinary PC" is just flat out wrong. The real issue that physicists are concerned about is whether the D-wave machine is a quantum computer or not. The issue is not whether quantum computers are "better" than classical ones. Assuming the correctness of quantum mechanics, a quantum computer WILL be faster than classical computers for specific classes of problems, exponentially faster in some cases. This has been mathematically proven. (EDIT: No it hasn't apparently. See Michael Nielsen's response below.)
- michael_nielsen 12y ago
  Your first paragraph is quite right. But the second paragraph is wrong: for (non-oracle) problems quantum computers are merely suspected to be faster in principle than conventional classical computers. It's never been proven.
  - Xcelerate 12y ago
    I guess I'm confused then. I thought that quantum algorithms had been proven to be faster than the best known classical algorithms (for instance, Shor's factorization), assuming the correctness and completeness of the postulates of QM. In other words, the order of the algorithm is derivable from the postulates. Is that not the case? I think there's a few people (t'Hooft if I remember correctly?) that believe a quantum computer will never be able to experimentally demonstrate this speed-up because some aspect of quantum mechanics is incomplete/incorrect. Edit: Here's the thread I was thinking of where t'Hooft and Shor discuss this http://physics.stackexchange.com/questions/34217/why-do-people-categorically-dismiss-some-simple-quantum-models http://physics.stackexchange.com/questions/34217/why-do-peop...
    - michael_nielsen 12y ago
      Shor's algorithm is exponentially faster than the best existing classical algorithm for factoring. But that doesn't mean there's not an exponentially faster classical algorithm which would be comparable in speed to Shor's algorithm. Some noted experts believe this is possible, and even likely. Richard Lipton believes it, and claims that Peter Sarnak does too: http://rjlipton.wordpress.com/2013/04/27/sex-lies-and-quantum-computers/ http://rjlipton.wordpress.com/2013/04/27/sex-lies-and-quantu... Yes, 't Hooft and others, including Leonid Levin and Oded Goldreich, believe that quantum computers won't function because of quantum mechanics breaking down. See, e.g.: http://www.wisdom.weizmann.ac.il/~oded/on-qc.html http://www.wisdom.weizmann.ac.il/~oded/on-qc.html http://www.cs.bu.edu/fac/lnd/expo/qc.htm http://www.cs.bu.edu/fac/lnd/expo/qc.htm
deleted 12y ago
[deleted]
dm2 12y ago
Here is another article today bashing the D-Wave Two computers: http://www.wired.com/2013/06/d-wave-quantum-computer-usc/ http://www.wired.com/2013/06/d-wave-quantum-computer-usc/ These machines are testing a completely new computing concept. We're trying to learn how they work so that we can apply that to building machines that can actually outperform traditional computers, and once that's achieved then the potential benefit will be enormous. According to http://www.dwavesys.com/d-wave-two-system http://www.dwavesys.com/d-wave-two-system as you scale up qubits the power demands do not increase. That alone has huge potential. Maybe new materials need to be developed to see the full potential of these computers, lots of research needs to be done. Why are all of these articles so pessimistic? NASA, Lockheed, and Google purchasing these multi-million dollar machines should indicate that there is at-least some potential and value in the D-Wave computers, even if in the end they just learn what D-Wave did wrong. https://www.youtube.com/watch?v=CMdHDHEuOUE https://www.youtube.com/watch?v=CMdHDHEuOUE "We don't know the best questions to ask the quantum computers, that's what we're trying to find out now."
- JoeAltmaier 12y ago
  So negative because there's still a non-zero probability that its not going to work at all, ever. That there's something about quantum computing we've figured out wrong, and no benefit is possible.
  - VonGuard 12y ago
    They're also negative because no one has actually proved that the D-Wave is, in fact, doing any actual quantum computing. That's been the issue all along with D-Wave: no one can prove that it's really doing anything with those qbits.
    - dm2 12y ago
      It depends on your definition of quantum computing, the D-Wave does http://en.wikipedia.org/wiki/Quantum_annealing http://en.wikipedia.org/wiki/Quantum_annealing and has been faster in some applications. https://plus.google.com/+QuantumAILab/posts https://plus.google.com/+QuantumAILab/posts They're just getting started, this field is very new, very difficult, and there are a lot of very smart people trying to answer the what/how/why/where/when of "quantum" computers. The hardware outperforms off-the-shelf solvers by a large margin "In an early test we dialed up random instances and pitted the machine against popular of-the-shelf solvers -- Tabu Search, Akmaxsat and CPLEX. At 509 qubits, the machine is about 35,500 times (!) faster than the best of these solvers. (You may have heard about a 3,600-fold speedup earlier, but that was on an older chip with only 439 qubits." [1] [1] https://plus.google.com/+QuantumAILab/posts/DymNo8DzAYi https://plus.google.com/+QuantumAILab/posts/DymNo8DzAYi
ColinWright 12y ago
Also: https://news.ycombinator.com/item?id=7917482 https://news.ycombinator.com/item?id=7917482 https://news.ycombinator.com/item?id=7917749 https://news.ycombinator.com/item?id=7917749
icegreentea 12y ago
This is the paper in question: http://www.sciencemag.org/content/early/2014/06/18/science.1252319 http://www.sciencemag.org/content/early/2014/06/18/science.1... Which appears (I can't tell, paywalled) to be an update or this one: http://arxiv.org/abs/1401.2910 http://arxiv.org/abs/1401.2910 I don't have to time to read the article properly right now, but doesn't look like they did anything ridiculous in their choice of testing algorithm.
robgibbons 12y ago
Firstly, this is the first of a new class of computers, so I am not surprised it may be slow at first. Secondly, this machine uses a relatively small number of bits, compared to a classical computer. Lastly, they're throwing classical problems at a quantum processor and wondering why it's not magically faster. I would like to see how an optimized quantum algorithm performs.
owenversteeg 12y ago
Original article: http://www.livescience.com/46414-first-quantum-computer-no-faster.html http://www.livescience.com/46414-first-quantum-computer-no-f...
MrBuddyCasino 12y ago
Previously: https://news.ycombinator.com/item?id=7917749 https://news.ycombinator.com/item?id=7917749
michaelochurch 12y ago
Weird title. If someone built a quantum computer that performed remotely as well as a 2014-era classical machine, that would be huge news. Quantum computers are really hard to build.
yellowapple 12y ago
What's the definition of "ordinary PC" being used? Not finding an answer to that in the article, which makes it difficult to get an idea of what the researchers are comparing this thing to.
- Bakkot 12y ago
  One which doesn't exploit quantum-mechanical principles of computation.
  - acjohnson55 12y ago
    Wouldn't that be a classical computer? PC is a weird term to use here.
  - yellowapple 12y ago
    So is that a brand-new Dell XPS machine? Is that my aging-not-too-well Compaq Presario 1210 with a Pentium? Is that a Macbook Air? Is that one of Oracle's $200,000 M-series servers? Is that some beige-box piece of junk that the researchers found in their neighbor's backyard? The category "personal computers which do not exploit quantum-mechanical principles of computation" is so mind-bogglingly vast that such a description alone is hardly useful.
bwy 12y ago
A few other comments have pointed it out already, but how does this comparison actually mean anything? For example, multiplication with the first hole-punch computers was no faster than multiplying by hand and paper (probably slower), but look where we are now!

46 points by aasarava 12y ago

The title is slightly misleading. This article is only talking about the performance of one specific quantum computer. (The D-Wave Two).

VonGuard 12y ago
Are there others that you can buy? As far as I know, D-Wave is the only one out of the lab. I'm totally a D-Wave skeptic, but I do have to state that the scientists who tested this thing sound like idiots, unless they really did try quantum annealing. If the D-Wave guys say they tried the wrong set of equations for the device, I'm inclined to believe them. Even though I don't even believe this thing is really a quantum computer, there are much more specific and defined ways to poke holes in D-Wave than just by running some tests and comparing speed. D-Wave has, very specifically, targeted this machine at one function: http://en.wikipedia.org/wiki/Quantum_annealing http://en.wikipedia.org/wiki/Quantum_annealing Unless you're doing quantum annealing on the D-Wave, it might as well be a toaster, an Android phone, or a Windows PC. It's made to do only quantum annealing. Did D-Wave 2 somehow expand its capabilities? I'm basing this on D-Wave 1 knowledge, but I cannot imagine anything really changed except the number of Qbits inside the thing. All this having been said, the D-Wave has yet to prove that it is even doing Quantum Annealing, let alone that it's faster than a traditional computer at this problem set. No one has shown it to be faster than traditional outside of D-Wave.
- mpthrapp 12y ago
  I'm not as up on Quantum Computing as I'd like to be, but the title seems to imply that QC as a concept is no faster than regular computing. Which may be true for general purpose computing, but that's never what QC was intended for.
- shoyer 12y ago
  Yes, of course they did what D-wave calls quantum annealing. As you say, that's all the D-Wave machines can do. The D-Wave executive's claim that the problems used in the study are "not at all the right choice for probing a quantum speedup" is in reference to the specific subtypes of quantum annealing problems that this study looked at, not whether they were doing quantum annealing at all.

Xcelerate 12y ago

The title of the article "Performance of quantum computer no better than ordinary PC" is just flat out wrong. The real issue that physicists are concerned about is whether the D-wave machine is a quantum computer or not. The issue is not whether quantum computers are "better" than classical ones. Assuming the correctness of quantum mechanics, a quantum computer WILL be faster than classical computers for specific classes of problems, exponentially faster in some cases. This has been mathematically proven. (EDIT: No it hasn't apparently. See Michael Nielsen's response below.)

michael_nielsen 12y ago
Your first paragraph is quite right. But the second paragraph is wrong: for (non-oracle) problems quantum computers are merely suspected to be faster in principle than conventional classical computers. It's never been proven.
- Xcelerate 12y ago
  I guess I'm confused then. I thought that quantum algorithms had been proven to be faster than the best known classical algorithms (for instance, Shor's factorization), assuming the correctness and completeness of the postulates of QM. In other words, the order of the algorithm is derivable from the postulates. Is that not the case? I think there's a few people (t'Hooft if I remember correctly?) that believe a quantum computer will never be able to experimentally demonstrate this speed-up because some aspect of quantum mechanics is incomplete/incorrect. Edit: Here's the thread I was thinking of where t'Hooft and Shor discuss this http://physics.stackexchange.com/questions/34217/why-do-people-categorically-dismiss-some-simple-quantum-models http://physics.stackexchange.com/questions/34217/why-do-peop...
  - michael_nielsen 12y ago
    Shor's algorithm is exponentially faster than the best existing classical algorithm for factoring. But that doesn't mean there's not an exponentially faster classical algorithm which would be comparable in speed to Shor's algorithm. Some noted experts believe this is possible, and even likely. Richard Lipton believes it, and claims that Peter Sarnak does too: http://rjlipton.wordpress.com/2013/04/27/sex-lies-and-quantum-computers/ http://rjlipton.wordpress.com/2013/04/27/sex-lies-and-quantu... Yes, 't Hooft and others, including Leonid Levin and Oded Goldreich, believe that quantum computers won't function because of quantum mechanics breaking down. See, e.g.: http://www.wisdom.weizmann.ac.il/~oded/on-qc.html http://www.wisdom.weizmann.ac.il/~oded/on-qc.html http://www.cs.bu.edu/fac/lnd/expo/qc.htm http://www.cs.bu.edu/fac/lnd/expo/qc.htm

deleted 12y ago

[deleted]

dm2 12y ago

Here is another article today bashing the D-Wave Two computers: http://www.wired.com/2013/06/d-wave-quantum-computer-usc/ http://www.wired.com/2013/06/d-wave-quantum-computer-usc/ These machines are testing a completely new computing concept. We're trying to learn how they work so that we can apply that to building machines that can actually outperform traditional computers, and once that's achieved then the potential benefit will be enormous. According to http://www.dwavesys.com/d-wave-two-system http://www.dwavesys.com/d-wave-two-system as you scale up qubits the power demands do not increase. That alone has huge potential. Maybe new materials need to be developed to see the full potential of these computers, lots of research needs to be done. Why are all of these articles so pessimistic? NASA, Lockheed, and Google purchasing these multi-million dollar machines should indicate that there is at-least some potential and value in the D-Wave computers, even if in the end they just learn what D-Wave did wrong. https://www.youtube.com/watch?v=CMdHDHEuOUE https://www.youtube.com/watch?v=CMdHDHEuOUE "We don't know the best questions to ask the quantum computers, that's what we're trying to find out now."

JoeAltmaier 12y ago
So negative because there's still a non-zero probability that its not going to work at all, ever. That there's something about quantum computing we've figured out wrong, and no benefit is possible.
- VonGuard 12y ago
  They're also negative because no one has actually proved that the D-Wave is, in fact, doing any actual quantum computing. That's been the issue all along with D-Wave: no one can prove that it's really doing anything with those qbits.
  - dm2 12y ago
    It depends on your definition of quantum computing, the D-Wave does http://en.wikipedia.org/wiki/Quantum_annealing http://en.wikipedia.org/wiki/Quantum_annealing and has been faster in some applications. https://plus.google.com/+QuantumAILab/posts https://plus.google.com/+QuantumAILab/posts They're just getting started, this field is very new, very difficult, and there are a lot of very smart people trying to answer the what/how/why/where/when of "quantum" computers. The hardware outperforms off-the-shelf solvers by a large margin "In an early test we dialed up random instances and pitted the machine against popular of-the-shelf solvers -- Tabu Search, Akmaxsat and CPLEX. At 509 qubits, the machine is about 35,500 times (!) faster than the best of these solvers. (You may have heard about a 3,600-fold speedup earlier, but that was on an older chip with only 439 qubits." [1] [1] https://plus.google.com/+QuantumAILab/posts/DymNo8DzAYi https://plus.google.com/+QuantumAILab/posts/DymNo8DzAYi

ColinWright 12y ago

Also: https://news.ycombinator.com/item?id=7917482 https://news.ycombinator.com/item?id=7917482 https://news.ycombinator.com/item?id=7917749 https://news.ycombinator.com/item?id=7917749

icegreentea 12y ago

This is the paper in question: http://www.sciencemag.org/content/early/2014/06/18/science.1252319 http://www.sciencemag.org/content/early/2014/06/18/science.1... Which appears (I can't tell, paywalled) to be an update or this one: http://arxiv.org/abs/1401.2910 http://arxiv.org/abs/1401.2910 I don't have to time to read the article properly right now, but doesn't look like they did anything ridiculous in their choice of testing algorithm.

robgibbons 12y ago

Firstly, this is the first of a new class of computers, so I am not surprised it may be slow at first. Secondly, this machine uses a relatively small number of bits, compared to a classical computer. Lastly, they're throwing classical problems at a quantum processor and wondering why it's not magically faster. I would like to see how an optimized quantum algorithm performs.

owenversteeg 12y ago

Original article: http://www.livescience.com/46414-first-quantum-computer-no-faster.html http://www.livescience.com/46414-first-quantum-computer-no-f...

MrBuddyCasino 12y ago

Previously: https://news.ycombinator.com/item?id=7917749 https://news.ycombinator.com/item?id=7917749

michaelochurch 12y ago

Weird title. If someone built a quantum computer that performed remotely as well as a 2014-era classical machine, that would be huge news. Quantum computers are really hard to build.

yellowapple 12y ago

What's the definition of "ordinary PC" being used? Not finding an answer to that in the article, which makes it difficult to get an idea of what the researchers are comparing this thing to.

Bakkot 12y ago
One which doesn't exploit quantum-mechanical principles of computation.
- acjohnson55 12y ago
  Wouldn't that be a classical computer? PC is a weird term to use here.
- yellowapple 12y ago
  So is that a brand-new Dell XPS machine? Is that my aging-not-too-well Compaq Presario 1210 with a Pentium? Is that a Macbook Air? Is that one of Oracle's $200,000 M-series servers? Is that some beige-box piece of junk that the researchers found in their neighbor's backyard? The category "personal computers which do not exploit quantum-mechanical principles of computation" is so mind-bogglingly vast that such a description alone is hardly useful.

bwy 12y ago

A few other comments have pointed it out already, but how does this comparison actually mean anything? For example, multiplication with the first hole-punch computers was no faster than multiplying by hand and paper (probably slower), but look where we are now!