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Re: quantum theory does need an interpretation

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  • Marchal
    Gary S. Bekkum wrote ... Thank you for refering us to this nice paper. (I communicate also the reference to the everything list where people could be
    Message 1 of 64 , Dec 31, 1969
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      Gary S. Bekkum wrote

      >I think that it is incorrect to make such sweeping assumptions linking
      >the mind to the quantum world as is often done in popular books. I am
      >not saying that I believe that the mind is a purely classical phenomena
      >either. I am only pointing out the many incompatible variations on the
      >"quantum mind" theme demonstrate that it is premature to join perception
      >to quantum theory.
      >Regarding your last point, there is a paper at the Los Alamos pre-print
      >archive, available in Adobe PDF format for the Adobe Reader (available
      >free at Adobe.com) that explains this in detail:
      >click on other formats, then select "create PDF"
      >Does Quantum Nonlocality Exist? Bell's Theorem and the
      >Many-Worlds Interpretation
      >Authors: Frank J. Tipler
      >Comments: 7 pages in plain TeX, no figures
      > "Quantum nonlocality may be an artifact of the assumption that
      >observers obey the laws of classical
      > mechanics, while observed systems obey quantum mechanics. I show
      >that, at least in the case of
      > Bell's Theorem, locality is restored if observed and observer are
      >both assumed to obey quantum
      > mechanics, as in the Many-Worlds Interpretation. Using the MWI, I
      >shall show that the apparently
      > "non-local" expectation value for the product of the spins of two
      >widely separated particles --- the
      > "quantum" part of Bell's Theorem --- is really due to a series of
      >three purely local measurements.
      > Thus, experiments confirming "nonlocality" are actually confirming
      >the MWI."

      Thank you for refering us to this nice paper. (I communicate also the
      reference to the everything list where people could be interested).
      Note that the idea that MWI restore locality is as old as Everett. In
      particular Everett makes that point clear in his big paper on the
      Universal Wave Function, when he looks at the EPR phenomenon from the
      multiverse point of view.
      But with Tipler's paper it is Bell's work itself which is under
      scrutiny with some clarity and rigor. That paper gives me the feeling
      that MWI restore also completely the classical use of counterfactual
      propositions. BTW it would be nice to see explicitely what happens with
      Kochen and Specker theorem in the MWI. In my opinion this shows that the
      MWI can be seen as a realist, local and determinist hidden variable
      interpretation of QM, where the hidden variables correspond to the
      universe where we momentarily belongs. It is so unfortunate that Everett
      meet Bohr and not Einstein :-( ... (I mean in our branch!).

    • Maurice Guernier
      ... Hi Babak, Thanks for the elaboration - I think I have a clearer idea now of what Mermin is saying. It seems that his view of the quantum state is similar
      Message 64 of 64 , Dec 8, 2009
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        --- In Fabric-of-Reality@yahoogroups.com, Babak Seradjeh <babaks@...> wrote:
        > On Mon, Dec 7, 2009 at 1:23 AM, Maurice Guernier <inntranz@...> wrote:
        > >
        > >
        > >
        > > I read Mermin's article and found I could agree with a lot of what he said, but I can't see it as a valid criticism of the ideas in FoR.
        > >
        > > But first I should explain my own point of view.
        > >
        > > Actually, it might also be Popper's view. Someone recently noted that Popper criticised the idea of "essence", saying that the important thing is not what something "is" (its essence), but what we can say about it - or words to that effect.
        > >
        > > [Unfortunately, I don't recall who posted this or what Popper actually said - so I would appreciate it if anyone can elaborate.]
        > You can find an account of this in Popper's intellectual
        > autobiography, Unended Quest, Sec. 7 pp. 18-31. He writes than in a
        > discussion with his father at 15 he reached an attitude that is
        > formulated in his "anti-essentialist exhortation":
        > "
        > Never let yourself be goaded into taking seriously problems about
        > words and their meanings. What must be taken seriously are questions
        > of fact, and assertions about facts: theories and hypotheses; the
        > problems they solve; and the problems they raise.
        > "
        > >
        > > A useful analogy for applying this idea to the interpretation of physics is to borrow the concept of "data" and "view" from the field of applied computer science.
        > > Here, the "data" represents the "what" (essence) and the "views" are the various ways the data can be presented (the interpretations) - such as a table of numbers, a graph, or even a pattern of electric charge in a memory chip.
        > > Any number of views are possible for a given set of data, and these views can even appear superficially contradictory - how can something be both a table and a graph?, how can an electron be a particle and a wave? - but we know they are actually just different descriptions of the same thing.
        > This last sentence is crucial. It means there is an underlying reality
        > which is described by the "data", irrespective of the "view". There's
        > nothing about our sensory perceptions (which is in fact quite
        > different for different "views"). The data does not describe these
        > perceptions, but a separate reality.
        > >
        > > In the same way, interpretations in physics are not exclusive.
        > > To the extent that they are valid representations of the underlying "data", no particular interpretation is privileged over any other in any absolute sense, but the value of each can be very different in subjective terms. Interpretations can vary in terms of how compatible they are with our psychology or in their usefulness for different purposes. Mathematical interpretations are good for making precise predictions whereas the physical view is easier for people to comprehend.
        > >
        > > If you believe this to be a useful way of looking at the world, then what do we make of statements like the following from David Mermin:
        > >
        > > > Notions like dimension or interval, or curvature or geodesics, are properties not of the
        > > > world we live in but of the abstract geometric constructions we have invented to help
        > > > us organize events."
        > >
        > > To be pedantic, it appears to contain its own contradiction. If "notions like dimension" are properties of "the abstract geometric constructions we have invented to help us organize events" then they are also properties of "world we live in" - just indirect ones.
        > > A more generous reading is that he is saying these things are interpretations - but if we accept what I suggested above, then so are all the other concepts we use to understand the world.
        > >
        > > It doesn't hurt to be reminded that "notions like dimension" are not "real" but rather are descriptions of something real.
        > > Then again, in a colloquial sense, if we don't use the word "real" for such things, the word has little practical use.
        > No, it doesn't hurt. But Mermin seems to take a much deeper position,
        > namely that our theories do not describe any reality separate from our
        > sensory perceptions. For notions like dimension, etc. not to be
        > properties of the world we live in, they must not descibe any real
        > thing in this world except our sensory perceptions. This is very
        > different from what you siad, with which I agree, about "data" and
        > "view".
        > >
        > > > But the other side of "I refute it thus" is to be suspicious of the reality of
        > > > those abstractions that help us impose coherence on our immediate perceptions.
        > >
        > > He says we should "be suspicious of the reality of those abstractions" and so we should.
        > > This isn't quite the same as fallibilism (which would require the substitution of "correctness" for "reality") - but in the same way that fallibilism doesn't mean we should reject the evidence of our senses, I don't see how it can follow from Mermin's argument that (for example) we should reject the idea that the quantum state is a useful interpretation of reality and instead consider it as a mere bookkeeping contrivance.
        > It does follow because then the quantum state not only has no reality
        > of its own but is not even a property of any reality outside our
        > minds. Mermin expresses it as following
        > "
        > Reifying the quantum state also induces people to write books and
        > organize conferences about "the quantum measurement problemErather
        > than acknowledging, with Werner Heisenberg, that "the discontinuous
        > change in the [quantum state] takes place ... because it is the
        > discontinuous change in our knowledge ... that has its image in the
        > discontinuous change of the [state].E>
        > [...] the recognition that quantum states are calculational devices
        > and not real properties of a system forces one to formulate the
        > sources of that discomfort in more nuanced, less sensational terms.
        > Taking that view of quantum states can diminish the motivation for
        > theoretical or experimental searches for a "mechanismEunderlying
        > "spooky actions at a distanceEor the "collapse of the
        > wavefunction"—searches that make life harder than it needs to be.

        Hi Babak,

        Thanks for the elaboration - I think I have a clearer idea now of what Mermin is saying.

        It seems that his view of the quantum state is similar to Dennett's on consciousness, or Dennett's example of the view, popular in the past, that there was some special quality about life that was reified as a "life force" or elan vital.
        Nowadays we view life as an emergent property of certain types of biological systems, taking away any role for a "life force".

        So I can respect Mermin's position in that I can understand how you might consider life force to be "not even a property of any reality outside our minds" - and by analogy that the same could apply to the quantum state.

        I can also see how unnecessary reification can result in a lot of wasted philosophising and "make life harder than it needs to be".

        But it seems a rather extreme view, particularly as the human mind seems to need these interpretations to help us make sense of what is going on. A bad habit possibly, but one we are likely stuck with.

        And I still don't see it as a criticism of the MWI. However we choose to interpret it, many worlds is still what quantum book-keeping predicts.


        > "
        > Babak
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