Howard Wiseman

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  • #1886
    Howard Wiseman
    Participant

    Well of course if you use different assumptions you can do the EPR argument very simply. The challenge is to read the EPR paper, and try to extract a rigorous argument from it, phrase by phrase, word by word, even. Or maybe I don’t understand what you mean by “primitive concepts”.

    Glad you agree with my own first paragraph. But I disagree with it. 🙂 What I should have said is that Bell knew he had an intuitive argument for determinism from predictability, not that he thought he had a proof.

    #1883
    Howard Wiseman
    Participant

    Matt

    Sure, I totally agree that the DAG intuition is why Bell thought he had proven determinism from predictability. But I guess we both agree that it would be completely unreasonable to allow that as an implicit assumption in a theorem, since orthodox quantum theory violates it. As I’ve always said, I am interested in Bell’s *theorem* of 1964, what he actually proved then.

    Your “Deterministic locality” is usually called “local determinism”, no? It includes both assumptions. “Separable predetermination” was actually the phrase Bell used in 1964. So I don’t think it makes sense to say that Bell assumed determinism and local determinism.

    Apart from that, your terminological suggestions are good. Except that you are leaving out Travis’ preferred option, that locality = the Einstein quote Bell gives. This is *not* the same as EPR’s assumptions. The EPR assumptions are quite convoluted. Read the Appendix of my 2014 paper if you want to get an idea how much work it is to actually prove things. There is no single localistic assumption in EPR, and at least one is implicit (i.e. never recognized by them).

    If we are going to talk about *theorems* then there should be some reasonably rigorous assumptions. Bell is really the first person to do that, when he writes down A(a,lambda). EPR come close, but, as I said, they sometimes use localistic assumptions implicitly. Einstein 1949 is clearer about locality, but vague. (He never says what it means for a system to have a “real physical situation”).

    So, from your “uncontroversial” list
    1. agree
    2. agree
    3. I don’t agree. I think he was probably aware that nobody had rigorously set out the assumptions needed for an EPR-argument, and so the only thing he would have claimed as a theorem was his own result from LD. This would explain why he always stated his theorem in terms of two assumptions in 1964 (and even 1971).
    4. I don’t agree. See above about how much work it is to make the EPR assumptions rigorous, and how there are missing assumptions.
    5. Yes. Bell’s version of EPR just doesn’t make sense.
    6. Yes. (Which is why I’m actually more interested in the future of Bell’s theorem, rather than the past, and I’ll have another paper out soon on causation).
    7. Yes. (And this is the message realists have to understand).
    8. Yes.
    7. Yes, but given I disagree with your point 3. So with my argument that Bell clearly intended his several-times-state notion of “locality” to be applicable to non-deterministic theories, I think my case for the [modern] version is very strong.

    Howard.

    #1874
    Howard Wiseman
    Participant

    Hi Travis,

    I don’t have anything to add to my reply under my article about why I think Bell gives his own definition of `locality’, and uses the referencing of Einstein as an appeal to authority to justify the reasonableness of making an assumption like this.

    In my formal reply I will give the quotes and both our opinions, and readers can make up their own mind.

    Howard.

    #1872
    Howard Wiseman
    Participant

    Hi Matt,

    I agree with some your comments here. But:

    1. Your discussion about DAGs is not really relevant to the physics community in 1964. Pearle’s first book was only published in the 1980s. No-one in physics was thinking this way in the 1960s. And in any case, the DAG model of causality is one that orthodox quantum mechanics fails to obey. So it would hardly be fair to allow it as an *implicit* assumption in Bell’s 1964 theorem!

    2. Your hypothetical is an interesting one. What would have happened would depend very much on the circumstances (Bell’s mood, how much free time he had, what else he had been thinking about …). So we’ll never know. I said in my 2014 paper: ” have no doubt that anyone familiar with BellĘĽs later work could have educed from Bell in 1964 the precise notion of LC … with little effort on eitherĘĽs part.” I am not building my interpretation on the basis that your option (1) was correct. My approach is not to try to guess what Bell might have come up with given the opportunity, but to make sense of the paper AS IT IS WRITTEN.

    3. I am actually being as *generous* as possible in allowing that Bell’s locality = PI. If someone wanted to argue “No, Bell made an even worse blunder than you think. The only concept of locality he had in mind was one that already presumed determinism.” then that would not change my basic position at all, which is that 1964 locality is not sufficient by itself to obtain a contradiction with QM, and so Bell’s 1964 theorem is not the same as his 1976 theorem.

    Howard.

    #1870
    Howard Wiseman
    Participant

    Sorry, another comment: Travis admits that Bell’s words in the EPR paragraph cannot be read as being a statement of local causality. That is why he says the paragraph “leaves something to be desired,” that it “disappoints” and is “problematic”. If it was all plausible that Bell’s words could be interpreted as being “local causality” then Travis would of course used that to tear down my whole case. But they cannot.

    I hope that convinces you Matt that it requires no special creativity to see that Bell’s localistic notion in 1964, interpreted to be applicable to probabilistic theories (as Bell thought it was), is PI, not LC.

    #1867
    Howard Wiseman
    Participant

    Hi all,
    Just a quick comment to say that, as per my original paper, and my reply paper, I do not at all agree that
    “… we can only speculate on how the 1964 Bell would have formally defined locality in a stochastic hidden variable theory. Since both parameter independence and local causality both reduce to exactly your equation (3) in the deterministic case, the mathematically rigorous part of the 1964 paper does not distinguish between those two possibilities. Hence any arguments that pick out one of those will always involve “pretty creative interpretation”.”

    The reason is simply that we have Bell’s own words for what he meant by locality:
    i) locality, or more precisely that the result of a measurement on one system be unaffected by operations on a distant system with which it has interacted in the past, that creates the essential difficulty
    ii) Now we make the hypothesis … that if the two measurements are made at places remote from one another the orientation of one magnet does not influence the result obtained with the other.
    iii) The vital assumption [2] is that the result $B$ for particle 2 does not depend on the setting $a$, of the magnet for particle 1, nor $A$ on $b$.
    iv) [one assumption is that] the setting of one measuring can[not] influence the reading of another instrument, however remote.

    None of these statements require determinism to make sense, and are unequivocally about the effect of an agent choice on one side affecting the measurement result on the other. That is, PI. They certainly cannot be read as a statement of local causality. If Bell had said “locality, or more precisely that the result of a measurement on one system be unaffected by distant events”, or “Now we make the hypothesis … that if the two measurements are made at places remote from one another the orientation of one magnet and the result obtained using it do not influence the result obtained with the other.” things would be very different. But he does not.

    Howard`

    #1609
    Howard Wiseman
    Participant

    Likewise (regarding posting early). Thanks for the stimulating piece Harvey and Chris – some interesting history and perspectives.

    I have a shorter question/comment than Travis: Why go so far as Everett’s theory as an example violating local causality (LC) but respecting locality/no-action-at-a-distance? Why not simply consider operational quantum mechanics, in which nothing exists but settings and outcomes. This satisfies Bell’s original concept of locality, at least once is formulated in the obvious way for probabilistic theories, as Jarrett and maybe others before him pointed out (as well as similar but more rigorously motivated concepts, but that’s a different topic.)

    Is it that you do not see operational QM as providing an explanation for the correlations it predicts, whereas you think Everettian QM does? I had some of the same concerns as Travis about the explanatory account you say that Everettian QM offers, regarding the difference between (0.9) and (0.10).

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