Why I Am Not a Psiontologist Speaker(s): Robert Spekkens
Abstract: The distinction between a realist interpretation of quantum theory that is psiontic and one that is psiepistemic is whether or not a difference in the quantum state necessarily implies a difference in the underlying ontic state. Psiontologists believe that it does, psiepistemicists that it does not. This talk will address the question of whether the PBR theorem should be interpreted as lending evidence against the psiepistemic research program. I will review the evidence in favour of the psiepistemic approach and describe the preexisting 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 psiepistemic position. The first assumption of the theorem  that holistic properties may exist for composite systems, but do not arise for unentangled quantum states  is only appealing if one is already predisposed to a psiontic view. The more natural assumption of separability (no holistic properties) coupled with the other assumptions of the theorem rules out both psiontic and psiepistemic models and so does not decide between them. The connection between the PBR theorem and other nogo 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 timeinversion of the PBR scenario.
Date: 08/05/2012  3:30 pm
Series: Quantum Foundations
