According to a paper published in Nature Google has developed a quantum computer.


The promise of quantum computers is that certain computational tasks might be executed exponentially faster on a quantum processor than on a classical processor. A fundamental challenge is to build a high-fidelity processor capable of running quantum algorithms in an exponentially large computational space. Here we report the use of a processor with programmable superconducting qubits to create quantum states on 53 qubits, corresponding to a computational state-space of dimension 2^53 (about 10^16).

Measurements from repeated experiments sample the resulting probability distribution, which we verify using classical simulations. Our Sycamore processor takes about 200 seconds to sample one instance of a quantum circuit a million times—our benchmarks currently indicate that the equivalent task for a state-of-the-art classical supercomputer would take approximately 10,000 years. This dramatic increase in speed compared to all known classical algorithms is an experimental realization of quantum supremacy for this specific computational task, heralding a much-anticipated computing paradigm.

On a cautionary note, Google's central claim, that they have performed in 200 seconds computation that would take current state-of-the-art supercomputers 10,000 years is disputed by IBM in a blog post which claims that:

We argue that an ideal simulation of the same task can be performed on a classical system in 2.5 days and with far greater fidelity. This is in fact a conservative, worst-case estimate, and we expect that with additional refinements the classical cost of the simulation can be further reduced.

3 minutes 20 seconds to perform what would take 2.5 days is still pretty impressive and presumably up-scaling would produce (exponentially) better results.

Note that quantum computing is not so well suited to linear processing, such as would typically be used to generate tablebases, but is ideally suited to highly parallel processes like those used in AlphaZero.

Does this advance mean we can look forward to a vastly improved AlphaZero?

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    I would guess it'll be several years, at least, before we see software like a chess app running on a quantum box. Nov 9, 2019 at 21:43
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    Google's quantum computer is not even really a proof-of-concept for a quantum computer that can do anything practical. Nov 9, 2019 at 22:16
  • Related: chess.stackexchange.com/questions/6147/…
    – Allure
    Nov 10, 2019 at 23:43
  • Not all problems can be sped up with a quantum computer. In particular, chess is PSPACE-hard, a class of problems not known to have faster quantum algorithms. Nov 12, 2019 at 17:05

2 Answers 2



Reasoning: Quantum Computers in the short to medium term only have some very specific things efficiently (factoring and discrete log and a few others). The algorithm google showed "quantum supremecy" on is basically simulating a random quantum circuit to generate random numbers, which is

  1. about as favorable an algorithm as you could imagine
  2. completely useless as an algorithm since there are plenty of simpler random number generators
  3. probably not even quantum supremecy achieved IBM paper

For general tasks, quantum computers achieve a quadratic speedup assuming a large enough quantum computer (compared to exponential or more speedup for the demonstrated problem). Furthermore, to even run a basic chess evaluation function on a quantum computer you would need at least an order of magnitude more qbits than state of the art (probably way more, but I'm hedging).

Overall, quantum computers now are at about the same stage as computers were in the 1800s. It will be a while before they are useful for anything, and chess is highly unlikely to be something they are ever used for seriously.


No! But maybe someday. Quantum computers are overhyped as much as AI. For the near future, they are a hope on the drawing board somewhere.

  • 2
    the fanboyz and bullies keep downvoting absolutely correct and useful answers. usually when they have no direct knowledge and go with what they wish were true. Feb 7, 2020 at 2:56
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    A good opinion, well reasoned and backed by correct information, is utterly useless if you don't provide said reasoning and information. "Show your work", as it were. This is Stack Exchange, not a forum.
    – Remellion
    Feb 7, 2020 at 13:22
  • the little up arrow only labels it as useful. The TRUTH is always useful. It is not my job to make you believe the truth. I present the facts and let you decide whether to take the road to the light or the darkness. AND this was NOT OPINION it was TRUTH from one who has been there for 50 years watching it and doing it. Feb 7, 2020 at 14:37
  • That's odd, because I hold the same opinion as you put forth in this answer, but see no facts you bring up supporting the conclusion that quantum computers are overhyped.
    – Remellion
    Feb 7, 2020 at 16:08
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    That is your opinion. As one working in the field I know it is FACT and it is useful. Feb 10, 2020 at 2:27

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