The quantum state cannot be interpreted statistically?

Anyone know if the PBR paper has been published, or at least accepted for publication yet?

This perhaps will never happen after the two of the authors in PBR has somewhat contradicted themselves in
http://xxx.lanl.gov/abs/1201.6554

I don’t really agree with your take on the PBR theorem. According to Harrgian and Spekkens, and also PBR, λ is supposed to be the full ontic state of the system. If the wavefunction is ontic in the model under consideration, then it is considered to be specified by λ and is not considered a separate variable. This is the reason why the term “ontic state” is used instead of “hidden variable state” because the latter is often interpreted to be variables in addition to the wavefunction. Most people would consider the wavefunction to be ontic in de Broglie-Bohm theory. I know there is some discussion of whether it should instead be regarded as nomological (lawlike) in the literature, but this is not really relevant here. The fact is, even if we know the exact values of the position variables in Bohm’s theory, we will still also need the wavefunction in addition to the position variables to compute the outcome probabilities for any experiment because it is needed to find the trajectories. Anything you need to compute the final outcome probabilities, over and above the primitive ontology (beables), is considered part of the ontic state by PBR by definition. You might not like that definition, but by using it we see that one feature of Bohmian theory is actually necessary for any hidden variable theory, namely that the wavefunction is ontic (in the sense of being required to compute the probabilities of any possible experiment). Therefore, Bohmians should be pretty happy about the PBR result as it vindicates one of their assumptions.

Also, I just wanted to note that I do not understand your discussion around eq. (10). Why do you think we can always replace a qubit state with one that has equal amplitudes up to a relative phase?

Anyone know if the PBR paper has been published, or at least accepted for publication yet?

There was an advance online publication in "Nature Physics" on May 6/12:

On the reality of the quantum state
http://www.nature.com/nphys/journal/...nphys2309.html

This talk will address the question of whether the PBR theorem should be interpreted as lending evidence against the psi-epistemic research program. I will review the evidence in favour of the psi-epistemic approach and describe the pre-existing reasons for thinking that if a quantum state represents knowledge about reality then it is not reality as we know it, i.e., it is not the kind of reality that is posited in the standard hidden variable framework. I will argue that the PBR theorem provides additional clues for "what has to give" in the hidden variable framework rather than providing a reason to retreat from the psi-epistemic position... The connection between the PBR theorem and other no-go results will be discussed. In particular, I will point out how the second assumption of the theorem is an instance of preparation noncontextuality, a property that is known not to be achievable in any ontological model of quantum theory, regardless of the status of separability (though not in the form posited by PBR). I will also consider the connection of PBR to the failure of local causality by considering an experimental scenario which is in a sense a time-inversion of the PBR scenario.

An interesting PhD thesis arguing for state realism that also discusses the recent PBR theorem quite a bit. Interesting, that one of the examiners for this thesis is Robert Spekkens:

The case for quantum state realism
http://ir.lib.uwo.ca/cgi/viewcontent...ype=additional

Generalisations of the recent Pusey-Barrett-Rudolph theorem for statistical models of quantum phenomena
http://xxx.lanl.gov/abs/1111.6304

The analysis of Pusey, Barrett and Rudolph aims to show there can be no objective physical reality which underlies, and is more general than, the state vector. But there appears to be a gap in their reasoning. To show their result, they use entangled states of independent systems. However, no specific experimental arrangement to detect these entangled states has been proposed. Thus their argument as it stands does not fully show there is a detectable conflict between the predictions of quantum mechanics and the existence of an underlying reality. And it is not clear that one can devise the necessary measuring device.