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QM Interpretations

  1. Oct 29, 2009 #1
    The following are the interpretations of QM:

    Bohmian · CCC · Consistent histories · Copenhagen · Ensemble · Hidden variable theory · Many-worlds · Pondicherry · Quantum logic · Relational · Transactional

    Which is the most accepted by the theoretical physics community? Obviously all have some supporters but I'm interested in finding out which is the most popular and why?

  2. jcsd
  3. Oct 29, 2009 #2


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    There have actually been surveys done on this here. And I have seen some informal surverys as well. In many ways the most popular answer may be "Don't know, not sure if I should care". Not saying that is my opinion or that most specialists hold that view, but I would say it reflects the viewpoint of a lot of working physicists.
  4. Oct 29, 2009 #3
    Ensemble, of course. It is not so opposite to the others though.

    Why ensemble? Because one point does not give you all information about the quantum state. One point is a too poor experiment. You cannot even tell/prove where it comes from.

    As in the macroscopic case, in the microscopic case you also deal with compound systems. And any compound system needs many exchanges to reveal its true face. More pixels, better image.
    Last edited: Oct 29, 2009
  5. Oct 29, 2009 #4


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    I find the majority of physicists don't care about interpretations, subscribing to Mermin's "shut up and calculate." Physics Today 57, #5, 10-11 (2004).
  6. Oct 30, 2009 #5
    They keep exactly to the ensemble interpretation: everybody calculates probabilities in our, single Universe according to the wave (quantum) mechanics.
    Last edited: Oct 30, 2009
  7. Oct 30, 2009 #6
    That's like saying that all agnostics are Buddhists, because Buddhism allows the possibility of all other gods.

    Among physicists who do express preference for an interpretation, many-worlds interpretation is very popular.
  8. Oct 30, 2009 #7


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    I never heard about CCC and Pondicherry. What are those? Some links?
  9. Oct 30, 2009 #8
    How about the experimentalists? Are they content with one-point data in a double-slit experiment or do they care about measurement statistics in this world?
  10. Oct 30, 2009 #9


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    I also prefer Many Worlds - and I am (or used to be) an instrumentalist/experimentalist. But I don't consider MW necessarily as "true", I only consider it as a very helpful mental picture to get some intuition for quantum-mechanical experiments. It avoids the difficult question of "what is a measurement" and "when does the wave function collapse" - and when you do so, all apparent paradoxes of EPR experiments and of retarded quantum erasers and so on disappear.
  11. Oct 30, 2009 #10
    Sorry to hear that.
  12. Oct 30, 2009 #11


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  13. Oct 30, 2009 #12
    So far many-worlds is my favorite. Is the fact that you have 12 interpretations of QM (and you may basically choose a favorite because one is not technically more correct than another) a major downfall to the theory?

  14. Oct 30, 2009 #13
    My opinion is that either MWI is true or QM itself is not exactly valid.
  15. Oct 30, 2009 #14


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    Remember that not everyone who is doing "QM experiments" are working in optics. The double slit is a nice "toy" but it is far from the only system where you can see "weird" quantum effects.
    There are plenty of people (me included) who work on system where there is only a single "quantum object" and not an ensemble, this includes just about everyone working with single qubits (solid state systems, ion traps etc).

    Personally I am in the "shut up and calculate" camp, and so is just about everyone else I work with.
  16. Oct 30, 2009 #15
    The more you will work with your "single quantum object", the more data you will analyse, the better you will understand what an "ensemble" means. It is an ensemble of data about your single system, it goes without saying, and that's why it is sufficient to shut up and calculate.
    Last edited: Oct 30, 2009
  17. Oct 30, 2009 #16


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    My opinion is that MWI is correct but not complete.
    (MWI by itself in its minimal form cannot explain the origin of the Born rule.)
  18. Oct 30, 2009 #17


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    True, but that is hardly a unique property of quantum systems. Most experiments involves taking averages of some sort at one point or another even if it just means increasing the integration time of your multimeter; but that has more to do with achieving a better signal-to-noise ratio than of any fundamental property of the system you are measuring.
    There are certainly examples where one can -at least in principle- see the "quantumness" of a systems using a single shot readout. An obvious example being to first manipulate a single using MW pulses and then reading out its state using a measurement pulse. Now, the final result of such a procedure is obviously single-valued (since the qubit will end up in one of two states) but what comes before that (the manipulation) is very much a series of "quantum operations".
    Any interpretation (or -in my case- lack of interpretation) should surely take into account not only what we see after the measurement pulse but also what is happening when we are manipulating the qubit; because even though we are not measuring we are certainly doing SOMETHING to the qubit with our pulses.
  19. Oct 30, 2009 #18


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    CCC = consciosness causes collapse

    Pondicherry interpretation: as I understand it, seems to be a variant of the instrumentalist interpretation - QM is nothing but a tool for calculating probabilities.

    Am I correct?
  20. Oct 30, 2009 #19
    There is a problem with Born rule. THere were claims that it hadbeen succesfully derived from 'pure' QM formalism, and another claims, that the derivation was circluar.

    But MWI is deterministic, so it is not clear what the 'probability' means in that context. So yes, there is some mystery, but I dont see it as a weakness, instead, it is a hint that we are missing something interesting about the reality.

    Then, the 'appearence' of the classical world is based on the Quantum Decoherence. QD has some difficulties:

    The choice of basic of decoherence is arbitrary. So you should define the basic based on some definition of the 'macroscopic system'. When 'macroscopic system' and basis are defined, you can define the 'branch'. But systems have different states, and in some branches we even dont exist! So the choice of a basic is branch-dependent.

    But these difficulties are rather technical: we dont know how the brain works, but it is not a fatal probalem for physics. So we can not correctly and completely define a 'state' and 'basis' or complicated system, but it is not fatal.

    And it is much better that that 'collapse' nonsense from CI - CI is absurd, it just cant be true.
  21. Oct 30, 2009 #20
    The missing part is simple: we have to recognize that even in a microscopic world we need many points of measurement to get some information. Information is not reduced to one point. On the contrary, the more points, the more accurate information about a system. Just like a photograph. The trick is that we think of microscopic world as of elementary, reducable-to-one-point world. It is this idea that fails.

    The classical world also "appears" as the inclusive picture (sum of many different QM events). Again, a photograph is a right example.
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