The “JVG algorithm” only wins on tiny numbers

(scottaaronson.blog)

77 points | by jhalderm 13 hours ago

7 comments

  • MathMonkeyMan 12 hours ago
    The title of this post changed as I was reading it. "It looks like the 'JVG algorithm' only wins on tiny numbers" is a charitable description. The article is Scott Aaronson lambasting the paper and shaming its authors as intellectual hooligans.
    • Strilanc 5 hours ago
      Agree. Scott is exactly correct when he just straight calls it crap.

      It's inaccurate to say it wins on small numbers because on small numbers you would use classical computers. By the time you get to numbers that take more than a minute to factor classically, and start dreaming of quantum computers, you're well beyond the size where you could tractably do the proposed state preparation.

      • bawolff 1 hour ago
        Honestly i think he was remarkably polite given the sort of crap we are talking about.
      • amelius 4 hours ago
        Well, the reviewers missed it too.
        • Strilanc 4 hours ago
          What reviewers? It's not a peer reviewed article.
    • measurablefunc 11 hours ago
      Scott Aaronson is the guy who keeps claiming quantum supremacy is here every year so he's like the proverbial pot calling the kettle black.
  • RcouF1uZ4gsC 12 hours ago
    Scott References the top comment on this previous HN discussion

    https://news.ycombinator.com/item?id=47246295

  • kittikitti 10 hours ago
    While I think the idea that claiming one can "precompute the xr mod N’s on a classical computer" sounds impractical there are a subset of problems where this might be valid. According to computational complexity theory, there's a class of algorithms called BQP (bounded-error quantum polynomial time).

    Shor's algorithm is part of BQP. Is the JVC algorithm part of BQP, even though it utilizes classical components? I think so.

    I believe that the precomputational step is the leading factor in the algorithm's time complexity, so it isn't technically a lower complexity than Shor's. If I had to speculate, there will be another class in quantum computational complexity theory that accommodates precomputation utilizing classical computing.

    I welcome the work, and after a quick scroll through the original paper, I think there is a great amount of additional research that could be done in this computational complexity class.

    • amluto 9 hours ago
      There is a genuinely interesting complexity class called BQP/poly, which is pronounced something like “bounded-error quantum polynomial time with classical advice” (add some more syllables for a complete pronunciation).

      The JVG algorithm is not a high quality example of this or really anything else. If you think of it as “classical advice”, then it fails, because the advice depends on the input and not just the size of the input. If you think of it as precomputation, it’s useless, because the precomputation involved already fully solves the discrete log problem. And the JVG paper doesn’t even explain how to run their circuit at respectable sizes without the sheer size of the circuit making the algorithm fail.

      It’s a bit like saying that one could optimize Stockfish to run 1000x faster by giving it an endgame table covering all 16-or-fewer-piece-positions. Sure, maybe you could, but you also already solved chess by the time you finish making that table.

    • adgjlsfhk1 9 hours ago
      JVC isn't BQP. it's exp time (I.e. worse than factoring without a quantum computer at all). it takes the only step of shors algorithm that is faster to run on a quantum computer and moves it to a classical computer
  • coolcoder9520 10 hours ago
    [flagged]
  • kmeisthax 12 hours ago
    I mean, considering that no quantum computer has ever actually factored a number, a speedup on tiny numbers is still impressive :P
    • dehrmann 10 hours ago
      I didn't get the quantum hype last year. At least with AI, you can see it do some impressive things with caveats, and there are bull and bear cases that are both reasonable. The quantum hype training is promising the world, but compared to AI, it's at the linear regression stage.
      • bawolff 1 hour ago
        Quantum computing is cool, but a lot of the people who were hyping it last year were absolute charletons. They were promosing things that quantum computers couldn't even do theoretically let alone next year. Even the more down to earth claims were stuff we are still 10-40 years away from presented as if its going to happen next month.

        Quantum computers are still cool and things worthy of research. Its going to be a very long road though. Where we are with quantum computers is like equivalent to where we were with regular computers in the 1800s.

        The hype people just make everything suck and should be ignored.

      • dekhn 10 hours ago
        It's a variation of nerd snipe. https://xkcd.com/356/

        People get taken by the theoretical coolness and ultimate utility of the idea, and assume it's just a matter of clever ideas and engineering to make it a reality. At some point, it becomes mandatory to work on it because the win would be so big it would make them famous and win all sorts of prizes and adulation.

        QC is far earlier than "linear regression" because linear regression worked right away when it was invented (reinvented multiple times, I think). Instead, with QC we have: an amazing theory based on our current understanding of physics, and the ability to build lab machines that exploit the theory, and some immediate applications were a powerful enough quantum computer built. On the other side, making one that beats a real computer for anything other than toy challenges is a huge engineering challenge, and every time somebody comes up with a QC that does something interesting, it spurs the classical computing folks to improve their results, which can be immediately applied on any number of off-the-shelf systems.

        • antonvs 4 hours ago
          > People get taken by the theoretical coolness and ultimate utility of the idea, and assume it's just a matter of clever ideas and engineering to make it a reality. At some point, it becomes mandatory to work on it because the win would be so big it would make them famous and win all sorts of prizes and adulation.

          Good description. Commercial fusion power seems to be in the same category currently.

          The next step once you have enough thinkers working on the problem is to start pretending that commercial success is merely a few years away, with 5 or 10 years being the ideal number.

    • adgjlsfhk1 10 hours ago
      The problem is that it's an exponential slowdown on large numbers.
    • Tyr42 12 hours ago
      Hey hey, 15 = 3*5 is factoring.
      • ashivkum 11 hours ago
        my understanding is that they factored 15 using a modular exponentiation circuit that presumes that the modulus is 3. factoring 15 with knowledge of 3 is not so impressive. Shor's algorithm has never been run with a full modular exponentiation circuit.
        • Strilanc 5 hours ago
          The very first demonstration of factoring 15 with a quantum computer, back in 2001, used a valid modular exponentiation circuit [1].

          The trickiest part of the circuit is they compile conditional multiplication by 4 (mod 15) into two controlled swaps. That's a very elegant way to do the multiplication, but most modular multiplication circuits are much more complex. 15 is a huge outlier on the difficulty of actually doing the modular exponentiation. Which is why so far 15 is the only number that's been factored by a quantum computer while meeting the bar of "yes you have to actually do the modular exponentiation required by Shor's algorithm".

          [1]: https://arxiv.org/pdf/quant-ph/0112176#page=15

          • adgjlsfhk1 1 hour ago
            would other mersenne numbers admit the same trick? if so, factoring 2047 would be really interesting to see. it's still well within the toy range, but it's big enough that it would be a lot easier to believe that the quantum computer was doing something (15 is so small that picking an odd number less than sqrt(15) is guaranteed to be a correct factorization)
  • guy4261 12 hours ago
    > (yes, the authors named it after themselves) The same way the AVL tree is named after its inventors - Georgy Adelson-Velsky and Evgenii Landis... Nothing peculiar about this imh
    • apnorton 6 hours ago
      This might not be something entirely obvious to people outside of academia, but the vast majority (which I'm only weakening a claim of "totality" in order to guard against unknown instances) of entities that bear the name of humans in the sciences do so because other people decided to call them by that name.

      From another view, Adelson-Velsky and Landis called their tree algorithm "an algorithm for the organization of information" (or, rather, they did so in Russian --- that's the English translation). RSA was called "a method" by Rivest, Shamir, and Adleman. Methods/algorithms/numbers/theorems/etc. generally are not given overly specific names in research papers, in part for practical reasons: researchers will develop many algorithms or theorems, but a very small proportion of these are actually relevant or interesting. Naming all of them would be a waste of time, so the names tend to be attached well after publication.

      To name something after oneself requires a degree of hubris that is looked down upon in the general academic community; the reason for this is that there is at least a facade (if not an actual belief) that one's involvement in the sciences should be for the pursuit of truth, not for the pursuit of fame. Naming something after yourself is, intrinsically, an action taken in the seeking of fame.

    • johncarlosbaez 11 hours ago
      Adelson-Velsky and Evgenii Landis were not the ones who named their tree the "AVL tree".

      In my "crackpot index", item 20 says:

      20 points for naming something after yourself. (E.g., talking about the "The Evans Field Equation" when your name happens to be Evans.)

      • ajkjk 9 hours ago
        https://math.ucr.edu/home/baez/crackpot.html for the curious (on that version it's item 25 though :o )
      • yccs27 3 hours ago
        The last line of the introduction

        > By doing so, we aim to provide a novel paradigm [...]

        also made me think of item 19 on your list:

        > 10 points for claiming that your work is on the cutting edge of a "paradigm shift".

        I'm sad though that you didn't call it the "Baez crackpot index"...

      • zahlman 10 hours ago
        I find it especially strange that two of the authors gave their first name to the algorithm.
      • goodmythical 11 hours ago
        Like RSA?
    • abound 12 hours ago
      Same with RSA and other things, I think the author's point is that slapping your name on an algorithm is a pretty big move (since practically, you can only do it a few times max in your life before it would get too confusing), and so it's a gaudy thing to do, especially for something illegitimate.
    • croes 11 hours ago
      Named after != named by
      • zimpenfish 5 hours ago
        > Named after != named by

        But also note that naming an algorithm, in and of itself, is fine; it's naming it after yoursel(f,ves) in the initial paper that's a sign of crackpottery.

        * Named by: Probably fine but heavily weighted on the grandiosity of the title.

        * Named after: Almost certainly fine (unless it's something like "X's Absolute Drivel Faced Garbage That Never Works Because X Kidnapped My Dog And Is A Moral Degenerate Algorithm", obvs.)

        * Named by yoursel(f,ves) after yoursel(f,ves): In the initial paper? Heavy likelihood of crackpottery. Years later? Egotistical but strong likelihood of being a useful algorithm.