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Is Quantum Mechanics an artifact of our ignorance?

  1. Aug 12, 2015 #1
    I've read a lot about QM and studied the math and how it work many and many times in several lectures in several places, but whenever I review what the theory says and compare it to how the measurement work, I come to doubt in the theory it self, I think it can even be explained using classical physics (note our measurement device are classical too), the uncertainty principle happens because when we do the measurement of position the distrub the state of the electron, (transfer the momentum because it's hitten by a photon, Campton scaterring), the infinite potential well work because a particle will bounce back and forward, measurement in different time yield in a wrong result, I think quantum mechanics work, but we are just saying stuff that happen to be true,but the theory seems like a story, it isn't the complete story, because we cannot much devices that distrubs our measurement, can some one tell me where did I go wrong?, need some serious help here :/ .
     
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  3. Aug 12, 2015 #2

    DrChinese

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    Are you familiar with the EPR paradox (1935) ? They attempted to show that quantum mechanics was incomplete by attacking the Heisenberg Uncertainty Principle (HUP). https://en.wikipedia.org/wiki/EPR_paradox

    However, in 1964 Bell showed that the EPR example was flawed and could not be reconciled with Quantum Mechanics. https://en.wikipedia.org/wiki/Bell's_theorem Subsequent experiments have shown the following:

    No physical theory of local Hidden Variables can ever reproduce all of the predictions of Quantum Mechanics.

    So basically, the idea that there is an observation limit due to "disturbing" particles cannot be correct. The HUP is the limit and there is no possibility of a more complete theory in the sense you describe. Here are some background references to assist you in understanding this conclusion (see bottom for links), which is a page I created for this: http://www.drchinese.com/David/Bell_Theorem.htm [Broken]
     
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  4. Aug 12, 2015 #3

    DrChinese

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  5. Aug 12, 2015 #4

    kith

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    I am not sure if I get you right but I want to talk a bit about what it means that the "measurement device is classical".

    As Heisenberg puts it: "The cut between what is considered to be part of the quantum system and what is considered to be part of the classical side can be shifted. The dividing line between the system to be observed and the measuring apparatus is immediately defined by the nature of the problem but it obviously signifies no discontinuity of the physical process. For this reason there must, within limits, exist complete freedom in choosing the position of the dividing line."

    Since QM doesn't suggest a physical limit beyond which it can't be applied we should be able to use a QM description for the measurement apparatus as well. And there a problem arises because letting the apparatus interact with the system doesn't yield a single outcome but a superposition of all possible outcomes.

    So your reasonable starting point, that the outcome just seems random because of the ignorance about the interaction between the apparatus and the system, doesn't seem to work.
     
  6. Aug 12, 2015 #5
    Yes, I got that, but I have a simpler question that can make things more clear, if we were a virus of just very small, can we still observe these quntum phenomena?, that virus may even obey a quantum mechanical rule, how would it feel to jump from a place to another (when a scientist does the expirement) or to pop out from the vaccum ?, or when we look at the universe from a far can we stars that seem so small obey quantum rules ?, I know this is out of topic, but just want to see the range of QM, Thanks !!
     
  7. Aug 12, 2015 #6

    bhobba

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    Well all those things you say, while common in popularisations, or even some beginning texts, are in fact incorrect eg quantum objects do not jump from place to place. We could not have a virus small enough because it could not have the processes necessary for life.

    If you want to understand QM here is a modern way to view it:
    http://www.scottaaronson.com/democritus/lec9.html

    These days its viewed as simply an extension of probability theory.

    Thanks
    Bill
     
  8. Aug 12, 2015 #7

    Nugatory

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  9. Aug 12, 2015 #8

    atyy

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    If there is only one outcome for each measurement and no hidden variables, QM cannot be an artifact of our ignorance.

    If there is only one outcome for each measurement and hidden variables, there is no known argument that QM cannot be an artifact of our ignorance. For non-relativistic QM, Bohmian Mechanics is an example of a theory in which QM arises as an artifact of our ignorance. Hidden variables that reproduce the predictions must be nonlocal or retrocausal or superdeterministic or ...

    If there are multiple outcomes for each measurement and no hidden variables, the Many-Worlds approach tries to make it seem that QM is an artifact of our ignorance.
     
    Last edited: Aug 12, 2015
  10. Aug 17, 2015 #9

    DrChinese

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    Thanks, hopefully the link helps. :)

    Yes, measurements of different things would give different probabilities than the 25%. So mass/energy would not work. It needs to be 2 non-commuting attributes (or components thereof). For any particles: position/momentum, or orthogonal spins.

    Handling the "perfect" correlation cases (a la EPR) is easy. The impossible part is finding and matching a Bell Inequality.
     
  11. Aug 17, 2015 #10
    So a physical (non-quantum) answer would be something I should communicate.

    I understand that is rather veiled and feel free to laugh. Almost always, later, a substantive math error is found. I'll check my numbers, but at the moment, I think the probabilities I see seem to match the Bell inequality. I readily accept that the most likely explanation is a math error. I was not concerned that my data is not a result of non-commuting attributes. Only that it matched the probabilities of the Bell inequality. I will look at it again later.
     
  12. Aug 18, 2015 #11
    Quantum mechanics in real then, it's a very disturbing and enermously un-intuitive fact, but I somewhat enjoy it, the detective who is allways guessing where the particle is following its foot prints, but there's no freaking foot-prints !, there's only an empty road (potential) and you should manage to work it out !, Thanks guys from making the concepts clear, I enjoyed reading all the articles you proposed !
     
  13. Aug 18, 2015 #12

    QST

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    It seems to me that QM is very much a result of our ignorance. It poses more questions than it brings solutions. The reason we have not been able to come up with a GUT is because all the pieces of the puzzle are not yet "found". QM is only a partial understanding and thus derives its "existence" from our ignorance.
     
  14. Aug 18, 2015 #13

    ZapperZ

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    But this is an "objection" not based on any empirical evidence, but instead, based on a matter of tastes! The fact that more and more experiments that are testing the validity of QM (check out the experiments testing "realism") are giving results consistent with QM's prediction are clear evidence that your view has no empirical basis.

    Zz.
     
  15. Aug 18, 2015 #14
    It has already been shown that "hidden variables" ( meaning our ignorance of relevant aspects ) are not able to reproduce the predictions of QM. Bells theorem shows the above to be incorrect.
     
  16. Aug 18, 2015 #15

    atyy

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    There are two similar but different ideas about the incompleteness of our current QM theories. Both cases are similar in that we suspect an incompleteness based on theoretical grounds alone, rather than any disagreement with present experimental data.

    1) The first incompleteness is related to the GUT problem you mention. Here the standard Wilsonian view is that the standard model of particle physics is incomplete. However, this "completion" may still be a quantum theory, but with different degrees of freedom.

    2) The second incompleteness is related to QM itself, ie. even if we find a quantum GUT that works, is quantum theory itself incomplete? Many have suspected it to be, because of the so-called "measurement problem". This includes Einstein (whose argument for it was wrong) and Dirac, as well as the many who find many-worlds an intriguing approach. Here one should not take "incompleteness" too literally as the solution to the "measurement problem". If many-worlds does work, then quantum mechanics is complete, but each measurement we make has more than one outcome.
     
  17. Aug 18, 2015 #16

    QST

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    My comment re: QM being a result of our ignorance has nothing to do with taste or opinion; it has to do with the definition of ignorance. It doesn't matter how many experiments verify QM's predictions; it is still a limited understanding. It does not give the whole picture.
     
  18. Aug 18, 2015 #17
    Today we can say with near certainty that most features of quantum theory are not an artefact of our ignorance. Those are for example the superposition principle, the uncertainty of non-commuting observables or the non-locality of entanglement.

    However, other aspects that contribute to the generally perceived "weirdness" of quantum theory and that are usually collectively named the "measurement problem" may very well be related to subjective ignorance. If that is really so will likely be decided by future research. So quantum theory may become somewhat less weird, but it will never be anything like classical physics.

    Cheers,

    Jazz
     
  19. Aug 18, 2015 #18
    In what way exactly is it lacking ?
     
  20. Aug 18, 2015 #19

    ZapperZ

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    But you don't know that because you are making an assumption that there is such a thing as the whole picture and that we don't have access to it. You've made an a priori assumption, and I'm showing you that there is no physical evidence that your assumption is correct. You certainly haven't offered any evidence that it is.

    Zz.
     
  21. Aug 18, 2015 #20

    ZapperZ

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    I agree. Unfortunately, some people used the term "weird" as if it is a valid evidence against something such as QM without realizing that it is a description based on a matter of tastes. There are many things that some people find weird but others find to be common. This is precisely the description based on a matter of tastes. QST doesn't seem to be aware of this.

    Zz.
     
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