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I What is the explanation for quantum correlations?

  1. Dec 10, 2015 #1
    Does a valid experimentally verified scientific explanation exists for the phenomena of quantum entanglement?

    Doesn't Quantum correlations demand explanations? What is the explanation for Quantum correlations? Is it,

    1. Retro-causation
    2. FTL
    3. Information is finite and far more fundamental than matter.
    4. Inter-connectedness outside of space-time.
    5. Super-determinism

    Doesn't the Schroedinger's cat thought experiment show the absurdity of the Copenhagen Interpretation?



    What is the explanation for quantum correlations?
     
  2. jcsd
  3. Dec 10, 2015 #2

    bhobba

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    Of course it does. I and others have posted it many times.

    So here we go again.

    Entanglement is nothing mysterious, its simply an extension of the principle of superposition to different systems. Suppose two systems can be in state |a> and |b>. If system 1 is in state |a> and system 2 is in state |b> that is written as |a>|b>. If system 1 is in state |b> and system 2 is in state |a> that is written as |b>|a>. But we now apply the principle of superposition so that c1*|a>|b> + c2*|b>|a> is a possible state. The systems are entangled - neither system 1 or system 2 are in a definite state - its in a peculiar non-classical state the combined systems are in.

    Because the only possible outcomes are |a>|b> or |b>|a> if you observe system 1 and get state |a> then you know system 2 is in state |b>, and similarly if you observe system 1 and get |b> you know system 2 is in state |a>. That's all entanglement is - a correlation. That's it, that's all. Let that sink in.

    Imagine you have two slips of paper a red and a green one and put them in envelopes. Send one to the other side of universe and keep the other. Open the envelope and you see red - you immediately know the other is green, and conversely. Nothing weird or mysterious here. That's all that's going on with entanglement with a twist I will explain.

    Now for the QM twist. It turns out the paper analogy is not quite the same as QM. The correlation is a bit different - its still just a correlation - but has statistical properties different to the paper example. Why the difference? The difference is in QM things do not have properties until observed to have them, whereas the slips of paper remain red or green at all times. But what if we insist it's like the slips of paper - then it turns out you need some kind of non local superluminal communication. That's really weird. But there is nothing compelling anyone to insist its like the slips of paper - simply accept QM allows a different kind of correlation and things are no longer mysterious.

    There is nothing mysterious going on. QM explains exactly what's happening.

    Thanks
    Bill
     
  4. Dec 10, 2015 #3
    I would go farther and say that there is compelling evidence (Bell's Theorem + Aspect experiments) to insist that the slips of paper model be abandoned, but on the other hand I don't think there is any way to accept QM in a simple way. Whatever explanation is adopted for making the QM calculations invariably falls apart under closer scrutiny. There is a "just do the math" attitude but this inevitably ends up divorcing itself from physical context.

    QM predicts what will happen. I would contest that vanilla QM explains any of it in any satisfactory sense. I would point to the unresolved status of the interpretation of QM as evidence for this.
     
  5. Dec 10, 2015 #4
    As bhobba pointed out, non-classical states exist in superpositions, meaning their inherent quantum uncertainty is spread out and shared(entangled) in the environment with all the other states in the universe. Upon measurement the states get their definite values hence the correlations which are always there due to their quantum nature. We don't notice these all encompassing quantum correlations because(enter favorite interpretation).
     
  6. Dec 10, 2015 #5

    zonde

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    "simply accept" does really belong in scientific explanation, at least if it is not backed up by scientific consensus that is reached after thorough investigation of the question.
     
  7. Dec 10, 2015 #6

    bhobba

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    Simply accepting the consequences of a theory rather than making out there is more to it is very scientific.

    Thanks
    Bill
     
  8. Dec 10, 2015 #7

    bhobba

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    Of course it has to be abandoned. If its like the slips of paper then there has to be FTL communication which doesn't happen with the paper slips.

    The situation is simple - people make more complex than necessary - why - beats me.

    Thanks
    Bill
     
  9. Dec 10, 2015 #8

    zonde

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    Explanations are good when they can be tested experimentally. So far there seems to be no such explanation.
    But from the five you named I would say that only 2. can be scientifically investigated.

    As for now QM gives very reliable phenomenological description.
     
  10. Dec 10, 2015 #9

    bhobba

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    There is the explanation I gave and it can be and has been tested experimentally.

    Thanks
    Bill
     
  11. Dec 10, 2015 #10

    zonde

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    Agree.
    But you propose to simply accept "different kind of correlation". To this I do not agree.
     
  12. Dec 10, 2015 #11
    That attitude would have left Newton and contemporaries to accept Kepler's laws as they were and not bother investigating any deeper. More pertinently, it would have led the likes of Bohm and Bell and everyone else to accept the Copenhagen interpretation as it was, and we would never have different or new interpretations on this problem, or possibly even the magnetic moment of the electron if every part of the CI was internalized without question.

    The correlations "cry out for explanation", and human beings collectively and scientists in particular will never be satisfied to accept them as they are. Where their quests for explanation will lead is another matter.
     
  13. Dec 10, 2015 #12

    bhobba

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    I propose accepting the logical consequences of a theory.

    Thanks
    Bill
     
  14. Dec 10, 2015 #13

    bhobba

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    Newtons laws explained all that was then known as QM explains all that is now known.

    Thanks
    Bill
     
  15. Dec 10, 2015 #14

    zonde

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    And now you are "making out there is more to it".
     
  16. Dec 10, 2015 #15

    bhobba

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    Your logic escapes me.

    Thanks
    Bill
     
  17. Dec 10, 2015 #16
    This begs the question though. Suppose that our world was fully classical, we wouldn't even think of contesting the classical paradigm. No scientist before QM ever thought of contesting the classical paradigm: nobody said "we can't simply accept that our probability theory is this", or "we can't simply accept that statistical correlations behave like this". If I asked you why is this so, and the answer was "because that fit with our intuition while quantum mechanics doesn't", then you see that what is not scientific is this attitude of feeling comfortable with classical paradigms and unconfortable with quantum paradigms, it's just psychological bias.
     
  18. Dec 10, 2015 #17

    zonde

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    Aren't "probability theory" and "statistical correlations" a math theories?
     
  19. Dec 10, 2015 #18

    zonde

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    How is "different kind of correlation" a logical consequence of physics theory?
     
  20. Dec 10, 2015 #19

    bhobba

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    There is no such thing as a 'math theory' in physics ie just math and hence not real.

    Applied probability is based on mapping events to the Kolmogorov axioms.

    Thanks
    Bill
     
    Last edited: Dec 10, 2015
  21. Dec 10, 2015 #20

    bhobba

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    Take the statistical correlation of the slips of paper and the correlations of entangelement - they are different.

    That's Bells Theorem.

    Thanks
    Bill
     
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