Quantum Mechanics In Your Face

(Title shamelessly stolen from Sidney Coleman.) I’m back after a bit of insane traveling, looking forward to resuming regular blogging next week. Someone has to weigh in about BICEP, right?

In the meantime, here’s a video to keep you occupied: a recording of the World Science Festival panel on quantum mechanics I had previously mentioned.

David Albert is defending dynamical collapse formulations, Sheldon Goldstein stands up for hidden variables, I am promoting the many-worlds formulation, and Rüdiger Schack is in favor of QBism, a psi-epistemic approach. Brian Greene is the moderator, and has brought along some fancy animations. It’s an hour and a half of quantal goodness, so settle in for quite a ride.

Just as the panel was happening, my first official forays into quantum foundations were appearing on the arxiv: a paper with Charles Sebens on deriving the Born Rule in Everettian quantum mechanics, as well as a shorter conference proceeding.

No time to delve into the details here, but I promise to do so soon!

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14 Responses to Quantum Mechanics In Your Face

  1. Duane says:

    Caught this conference through someone else earlier. Just like to say that I was lost after about the first 10 minutes lol!

  2. Sorry to rain on the parade, but there is this itty-bitty problem with Born’s rule: is is not as universal as people like to think. The result is not well known, but there is this formulation of quantum mechanics rigorously equivalent with spinors and Dirac equation where a generalization happens: you go from probability to a 4-current probability density subject to a relativistic continuity condition. In the low speed limit you recover Born’s rule as expected, but there is more that meets the eye in Born’s rule. (and now for a shameless self promotion, expect an archive paper about this mid to late July 🙂 )

  3. Erik Bray says:

    Huh, you know, as a relative novice I had never given much thought to the question of deriving Born’s rule. It always just seemed “obvious” and yet now that I think about it I find that pretty unsatisfying. Especially, if what Florin suggests is true, if it doesn’t apply universally.

    Thanks for posting the video. I look forward to watching it.

  4. I note that this is the same video you embedded in your previous post, except this time (a) it’s on Youtube, and (b) the introductory speech at the beginning has been stripped out.

    Surely it would be appropriate to mention this in the post?

    Anyway, on the subject, I thought the video was an excellent explainer (except for the QB part, which made no sense whatsoever).

    An analogy for an interpretation similar to Sheldon Goldstein’s is that every point in the universe is a hotel, a particle is a travelling celebrity, and the wave consists of the particle’s agents, whose job it is to find it a room for the night…

  5. merlin says:

    Like to push the boundaries of science and technology using logical deduction and what we can improve to do it

  6. kashyap vasavada says:

    @Florin Moldoveanu ;
    Is there a known experimental violation of Born rule?

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  8. James Gallagher says:


    Good luck with that, I suppose, like the Bohmians, you’ll be looking for evidence of Born rule violations in the Cosmic Microwave Background? Or maybe from Gamma Ray Bursts or the LHC measurements?

    Well, as I said, good luck anyway! 🙂

  9. David Redfrost says:

    Just read “Many worlds”. As a poet I want to recast the language however obtuse it is, but I’m troubled that you are venturing into metaphysics here as I understand it, poorly. Perhaps you could put it into more crude language so I can smooth it out for you. Good luck anyway. I do enjoy reading your posts.

  10. John Barrett says:

    Would you mind explaining that first paper in English please? I didn’t get it. It seemed like it could help me with a problem I have been having. I started going for flushes in Texas Hold’em, but it is like the universe itself caught on to my little secret. I figured, since I already had the first three cards of the flush, it wouldn’t change the chances of me getting the last card of the flush. Then about 1 in every 4 cards of the deck should still be of that suit. I should have a 1 in 4 chance of landing the flush on the river.

    It worked for a day or so, and I won a lot of fake money doing that online. Then I tried doing the same thing for real money, and it seemed like someone could get a full boat on me drawing on the river with only about 4 outs (that was a lot less of a chance than my 1 in 4). Then this seemed to happen to me every time someone tried it, but when I tried going for something like that on the river, I would never get it myself 🙁

    It could be like when Monty ask you to pick a door 1, 2, or 3. You pick door number 1 so then you have a 1/3 chance of getting it right. He reveals door number 3 and you see the donkey. He then tells you that you can switch doors or take the money. Then since there are only 2 doors left, switching would give you a 50/50 chance of getting it right, since there are only 2 doors. Then Monty had to reveal one of the donkeys. Do you still have a 50/50 chance by just having the choice and not making it?

  11. Michael Weissman says:

    That Born paper looks nice enough until it takes the Zurek turn at the end. There are severe problems with that argument. It simply assumes that there must be some context-free sensible intersubjectively agreed probability, the same one that would (almost) be obtained if a certain counterfactual decoherence process occurred. Once you make those assumptions, the traditional arguments for the Born rule as the only possible one suffice. Unfortunately, those assumptions are precisely what one cannot get from a simple reading of quantum formalism. If the formalism was all one knew, they would be shocking results. So here’s an alternative argument , a twist on one made originally by Jacques Mallah . Regardless of the likelihood that this alternative won’t hold up, it has a more complete criticism of the type of argument you give,

  12. James C. says:

    Pop-physics premature “many worlds” blathering is what theorists do to make money once they’ve realized they will be unable to do anything with quantum gravity. The fact that Brian Greene was involved in this says everything you need to know

  13. tomh says:

    “Do you still have a 50/50 chance by just having the choice and not making it?”


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