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Is it possible to complete QuantumTheory by Hidden Variables?

  1. Sep 5, 2004 #1
    I think that fon Neumann's Theorem about unpossibility of Hidden Variables does not include the all kind of Hidden Variables. There is HV, which does not have the corresponding to one operator to one quantitative which measurable. In addition Bell's Inequality does not include this class of Hidden Variables. Is it opinion only mine or anymore can agree?
     
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  3. Sep 5, 2004 #2

    ZapperZ

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    What EXPERIMENTAL evidence is there to indicate that quantum theory is "incomplete"?

    When we say that something is incomplete, it means that there are phenomena or observations that cannot be explained within that formalism. Classical mechanics is incomplete because we know of many observations that it cannot describe. There are no such observations for quantum mechanics.

    Without those, why is there a need to make it "complete"? And without those, all of these are simply based on a matter of "tastes". This is not a valid argument against ANY ideas in physics, much less quantum mechanics.

    Zz.
     
  4. Sep 5, 2004 #3
    Any theory is incomplete. I can not see anyone who was say that Quantum Theory is complete. Can you say that Quantum Theory is complete now?
     
  5. Sep 5, 2004 #4

    ZapperZ

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    You might as well say that all of PHYSICS is incomplete and get it over with.

    The progress we have made in physics are due to the fact that along the way, we find NEW things which are beyond existing understanding. We did not make any progress by simply blurting to the world that so-and-so is incomplete. What you just stated are what I called a matter of tastes. Physics cannot and should not be challenged this way. You might as well say quantum mechanics is incomplete because your favorite color is blue.

    I ask you again, what possible impetus and observation do you have to indicate that quantum mechanics is incomplete?

    Zz.
     
  6. Sep 5, 2004 #5
    You are do not answer to my question. In the same time I do not like your question because I'm understand that you are ask me the provocation question but this is...
    Many, many and many in Quantum Theory. The first is Quantum Axiomatic.
    The second is Quantum teleportation with the speed of more than the light velocity. 3-th is a fantasy about unlocality of Quantum Theory because it is possible to interpretive unlocality with another... 4-th is interpretation of the mass particle, which spread, in the whole world. And so on very long. The all of experiments can be describe with another interpretation. We can agree with experiments but does not agree with Quantum theory. So much interpretations it is possible you are known.
     
    Last edited: Sep 5, 2004
  7. Sep 5, 2004 #6

    ZapperZ

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    We have a language problem (I barely understood half of what you typed).

    ALL that you have listed have NOT shown a single incorrect observation inconsistent with quantum theory. What you appear to have a problem with is the INTERPRETATION of quantum theory. There is a difference here!

    Look again at ANY of the so-called objections you have. Figure out if these are really "experimental observation" or simply a matter of preference! Simply saying that there is another way to explain so-and-so phenomene means nothing, because you have to show how that other explanation can also be consistent with A WHOLE ZOO of other observations that QM has already described! Given that fact, I'd rather stick by QM since that single formulation has the ability to do a whole lot more than your alternative explanation.

    This last part isn't a matter of preference - it is rational logic.

    Zz.
     
  8. Sep 5, 2004 #7
    Yes. I agree with you in the most part. In the same time I see that I'm right. But where is answer to my question about possibility of Hidden Variables? It is the most my question but not about complete or no. It is Philosophy now only. It was the question in 1935 but not now because many years and many persons were write about complete or no.
     
  9. Sep 5, 2004 #8
    I think cartuz is referring to Quantum Information Theory and stuff like multi-universa.

    Cartuz, if i am right, please state your exact problem ??? What is it that gives you these impressions of QM.

    Remember that multi-universa are an interpretation of QM, just like the Standar-Copenhagen interpretation.

    regards
    marlon
     
  10. Sep 5, 2004 #9

    ZapperZ

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    No, I don't think you are correct in your original question, because I asked you repeatedly on what possible experimental evidence you have that will cause you to say that there could be these "hidden variables"? ALL of the EPR type experiments testing the Bell inequality (or the more stringent CHSH inequality) have confirmed what is consistent with QM!

    Now you can say this doesn't rule out some exotic hidden variables. I could also say it doesn't indicate they exist either! So now, without any experimental justification, this issue will be debated simply based on preferences - I call this a matter of tastes! Such debates do not belong in physics.

    Zz.
     
  11. Sep 5, 2004 #10
    I'm understand you, Marlon.
    In other words I think that QT must be derived from Classical Physics. But QT is operate with probability quantities and Classical Physics is no. Another way to us is to describe Classical Physics in the terms of Probability Theory. Of cause it is possible but it is do not like to me and to other.
     
  12. Sep 5, 2004 #11
    Nothing exotic there is. I use a random background of classical gravitational fields. Do not answer that it is weak. I 'm repeat my question one more in other words. Can we to employ fon Neumann's theorem and Bell's Inequalities for the all cases and types of Hidden Variables? Or no? I think no.
    And I disagree with you when you are identify Quantum Theory and Experimemt. It is not the same.
     
    Last edited: Sep 5, 2004
  13. Sep 5, 2004 #12

    ZapperZ

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    Sorry, can someone again translate this for me?

    Zz.
     
  14. Sep 5, 2004 #13
    Although Bell's inequality seems to invalidate local realism, there's a scientist called Franson that insists that this is not true, that local quantum mechanics with hidden variables is possible if we accept the concept of delayed determinism. Is delayed determinism a viable idea?
     
  15. Sep 5, 2004 #14

    ZapperZ

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    The problem here isn't that there are no other possible explanation for ALL the EPR-type experiment. The problem is how to determine which is correct!

    Till Bell came out with his formulation, the issue of EPR paradox was debated simply based on a matter of preference. People take camps based on what they feel comfortable with. With Bell's theorem, finally there is a way to TEST a certain part of the whole issue of non-local hidden variables. It is now no longer simply a matter of taste!

    Saying another "scenario" can explain so-and-so observation isn't saying much. This is because there is a whole zoo of EPR-experiments that are consistent with QM's predictions. And I haven't read any comments or rebuttals to all those papers regarding a different interpretation of those results. So those who are taking the alternative route haven't put their money where their mouths are. The ONLY weakly-viable discussion going on is the possibilty of a time-loophole in Bell's theorem (even this is highly disputed).

    Zz.
     
  16. Sep 7, 2004 #15
    To answer the original question, there is a hidden-variable theory called Bohmian Mechanics, which agrees with the predictions of quantum mechanics (as far as they are unambiguous). Look it up on Stanford Encyclopedia of Philosophy.

    As for the more general debate "is quantum mechanics complete and is this a matter for physics or philosophy?" I think that we can only say that the jury is still out on the subject. There are a growing number of physicists who think it is a matter of physics rather than philosophy. I am one of them, so let me explain why.

    In the standard axiomatization of quantum mechanics, measurement plays a special role, but the theory makes no mention of what constitutes a measurement, i.e. what causes the projection postulate to apply rather than the usual unitary dynamics. This is known as the measurement problem. Now, for (almost) all practical purposes, we have no problem determining what a measurement is and the predictions of quantum mechanics agree well with experiment. However, modern experiments, such as those on SQUID rings, involve superpositions of macroscopically large systems and measuring devices which are well described by quantum mechanics. We can see that the distinction between 'quantum system' and 'measuring device' has become blurred.

    Some approaches to the foundations of quantum theory make different predictions for the behaviour of such systems. For example, the 'spontaneous collapse' models predict a scale beyond which we cannot observe quantum coherences. Even Bohmian mechanics has a concept of 'non-equlibrium matter', which would behave differently from normal matter if it exists. We can see that these are actually different theories, with testable predictions, rather than mere 'interpretations', which is how they were originally seen. Since no theory invented by mankind has ever been the ultimate true theory of the universe, it is natural to assume that the same is true of quantum mechanics. To me it seems just as likely that new physics will emerge from ideas designed to deal with the conceptual difficulties of quantum mechanics as it is from other considerations.

    Even interpretations that do not make any different predictions from quantum mechanics may prove to be quite important. For example, many of them, such as consistent histories, Bohmian mechanics and many-worlds, suggest radically different ways of constructing a theory of quantum gravity. If the consequences of these theories are ever tested, it may be possible to sort out the question of 'interpretation' by experiment.

    Undoubtably there is interesting philosophy arising from interpretations of quantum mechanics, but it is not at all clear where the dividing line between physics and philosophy actually lies. I believe that in the next few years we will see questions that are traditionally regarded as philosophical becoming accepted as real physical problems. This is just my opinion of course, but hopefully time will tell us the answer rather than debates on message boards.
     
  17. Sep 7, 2004 #16

    ZapperZ

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    You have brought up several interesting issues. Unfortunately, I have time to address only one part of it since I'm trying to get ready to go off on a short vacation (thanks to Frances).

    The problem here is that by invoking Bohmiam mechanics, we are dragging in a whole set of other problems that shouldn't be overlooked. Till recently, the biggest drawback of Bohmian mechanics is that there's no way to for a formulation to include the creation and desctruction of particles. This means that Bohmian mechanics has almost no ability to be formulated into an equivalent form of QFT. This is a significant problem.

    Recently, a temporary remedy was presented.[1] However, it still includes a major problem in the fact that the remedy isn't lorentz invariant. This make the remedy almost useless.

    Thus, there still remain significant problems with Bohmian mechanics. I just want to make sure that it is understood by people who are not familiar with it that this isn't a done deal.

    Zz.

    [1] D. Durr et al., PRL v.93, p.090402 (2004).
     
  18. Sep 7, 2004 #17
    There should be no www. before stanford in the link.
     
  19. Sep 7, 2004 #18

    DrChinese

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    Key points of the Bell Theorem are often missed during discussions. Specifically, that Bell does not really attempt to prove or disprove QM. Bell effectively states: a) it is obvious that any replacement theory for QM should at least give results that replicate or exceed the results of QM; and b) that any such theory cannot be local realisitic (i.e. local with hidden variables).

    This cut to the heart of the EPR paper questioning the completeness of QM, which tacitly assumes that locality is fundamental. So it may be possible to complete QM by the addition of hidden variables which are NONLOCAL. (Of course this creates problems of its own.)
     
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