5 ms·

Even if the calibration process "cheats", why should we care? It's not like being practical is the goal. After the calibration is done, you still have a device

Even if the calibration process "cheats", why should we care? It's not like being practical is the goal. After the calibration is done, you still have a device that can do something believed intractable on classical computers. If it is possible for a classical computer to get comparable results just from a long calibration process, then that means the cross entropy test is flawed/limited, which is a separate argument.

lisper 7y ago
If you're going to allow cheating on calibration then it's trivial to achieve "quantum supremacy": simply precompute the answer and call that "calibration"!
- dooglius 7y ago
  There's no "answer" to precalculate, it's drawing from a distribution. Could you calibrate a non-quantum circuit to have a distribution passing the test? Supposedly, this is not possible even given arbitrary pre-computation time.
  - lisper 7y ago
    I can pre-calculate as many samples from the distribution as you can generate during the coherence time of the QC. Once you lose coherence, you have to re-calibrate, and during that time I can pre-compute another set of samples.
    - dooglius 7y ago
      That's true, if you pre-sample you can beat the test. Is that the effect you think the calibration is having? > Once you lose coherence, you have to re-calibrate I didn't realize this, where did you see that?
      - lisper 7y ago
        > Is that the effect you think the calibration is having? I have no idea. All I know (or at least I'm pretty sure of) is that you have to re-calibrate every time you lose coherence, otherwise it would not be calibration, it would be a one-time process that would be considered part of the construction of the QC. > where did you see that? Nowhere. I inferred it. It's possible that I'm wrong, but I'll give you long odds against. I have a pretty good understanding of how QCs work.
  - Barrin92 7y ago
    You can bring the complexity on a classical machine down to linear by allowing for large disk space, that is precisely the claim that IBM makes in response to the argument.
andrewla 7y ago
At issue, as I understand it, is whether the results from the 53-bit simulation (which would take 10,000 years, or 2.5 days, depending on who you believe) are valid or whether they are just so much junk because they haven't been calibrated and rely on calibrations that may or may not generalize. Kalai responds to Peter Shor making similar critiques in the comment threads in the blog, but it seems it comes down to clarifications on methodology, so may not be a fatal defect.

lisper 7y ago

If you're going to allow cheating on calibration then it's trivial to achieve "quantum supremacy": simply precompute the answer and call that "calibration"!

dooglius 7y ago
There's no "answer" to precalculate, it's drawing from a distribution. Could you calibrate a non-quantum circuit to have a distribution passing the test? Supposedly, this is not possible even given arbitrary pre-computation time.
- lisper 7y ago
  I can pre-calculate as many samples from the distribution as you can generate during the coherence time of the QC. Once you lose coherence, you have to re-calibrate, and during that time I can pre-compute another set of samples.
  - dooglius 7y ago
    That's true, if you pre-sample you can beat the test. Is that the effect you think the calibration is having? > Once you lose coherence, you have to re-calibrate I didn't realize this, where did you see that?
    - lisper 7y ago
      > Is that the effect you think the calibration is having? I have no idea. All I know (or at least I'm pretty sure of) is that you have to re-calibrate every time you lose coherence, otherwise it would not be calibration, it would be a one-time process that would be considered part of the construction of the QC. > where did you see that? Nowhere. I inferred it. It's possible that I'm wrong, but I'll give you long odds against. I have a pretty good understanding of how QCs work.
- Barrin92 7y ago
  You can bring the complexity on a classical machine down to linear by allowing for large disk space, that is precisely the claim that IBM makes in response to the argument.

andrewla 7y ago

At issue, as I understand it, is whether the results from the 53-bit simulation (which would take 10,000 years, or 2.5 days, depending on who you believe) are valid or whether they are just so much junk because they haven't been calibrated and rely on calibrations that may or may not generalize. Kalai responds to Peter Shor making similar critiques in the comment threads in the blog, but it seems it comes down to clarifications on methodology, so may not be a fatal defect.