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A Experimental tests on the reality of the quantum state

  1. Mar 19, 2017 #1
    Does this mean that we will one day have an answer to the old age question on the ontology of the wave function:
    Towards optimal experimental tests on the reality of the quantum state
  2. jcsd
  3. Mar 20, 2017 #2
    I suppose ontology is in the mind of the beholder. I was pretty convinced by the Bell Inequality experiments.
    I don't doubt the value of this research, but I suspect that anyone who was uncertain before will be no more certain now.
  4. Mar 20, 2017 #3


    Staff: Mentor

    We have interpretations where the state is like Bayesian probabilities and they imply the formalism of QM. The logic is dead simple (its just how you interpret the Born rule eg you can interpret it as Bayesian probabilities) so it's impossible, utterly impossible to show the wave-function is 'real'. If someone announces a proof of 1=0 I don't have to read it to know they divided by 0 somewhere. Same here - there is no way, its impossible, utterly impossible to discover the ontological status of the Quantum state unless QM is modified in some way AND that modification is experimentally proven.

    All this was pointed out in the famous PBR Theroem:
    Here we present a no-go theorem: if the quantum state merely represents information about the real physical state of a system, then experimental predictions are obtained which contradict those of quantum theory. The argument depends on few assumptions. One is that a system has a “real physical state” – not necessarily completely described by quantum theory, but objective and independent of the observer. This assumption only needs to hold for systems that are isolated, and not entangled with other systems. Nonetheless, this assumption, or some part of it, would be denied by instrumentalist approaches to quantum theory, wherein the quantum state is merely a calculational tool for making predictions concerning macroscopic measurement outcomes. The other main assumption is that systems that are prepared independently have independent physical states.

    Last edited: Mar 20, 2017
  5. Mar 20, 2017 #4


    Staff: Mentor

    I read a bit of the paper.

    He is proposing a modification of QM (specifically a hidden variable type model) that leads to the state being real. Its not QM proper - but an extension. Yes if that extension is proven then we can say its real.

    In other words he is proposing a model where its real and asking if experiment can confirm it.

    Of course that kind of 'process' can prove its real. But its hardly a surprising idea.

  6. Mar 22, 2017 #5

    Zafa Pi

    User Avatar
    Gold Member

    If my reading of the OP article and PBR are correct, then it seems your observation is right on.

    It comes to this: We can prove (using QM) the usual quantum state (of, say, a photon) is ontic (real) if we get to assume that photons have some ontic state (hidden variables) plus the independence condition.
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