jiri soucek,

I am somewhat sympathetic to the view that quantum theory should be understood in terms of some sort of non-Kolmogorovian probability theory. However, there are a couple of problems with this.

First, it is not just since 2008 that this option has existed. There are currently a few dozen competing generalized probability theories…[Read more]

Shan,

“In fact, the writing of this paper is mainly motivated by your words in your review paper. You said, “A straightforward resolution of the collapse of the wavefunction, the measurement problem, Schrodinger’s cat
and friends is one of the main advantages of psi-epistemic interpretations…. The measurement problem is not so much resolved by ps…[Read more]

Shan,

We have had so many discussions about this now that I am beginning to think that you are being deliberately obtuse, and trying to court controversy where there ought to be none.

Let me first note that not all ontological models solve the measurement problem, psi-epistemic or not. Some do and some don’t. Since Bohmian mechanics can be fit…[Read more]

One big objection to your argument is that, if true, it would imply that classical probability distributions are also properties of individual systems. The reason is that we can do the whole protective measurement scheme for Gaussian states using only Gaussian operations. Quantum mechanics with only Gaussian states and operations is equivalent…[Read more]

I think it is also probably possible to derive some sort of mathematical equivalence between the two types of protective measurement, i.e. to convert an adiabatic scheme into a Zeno scheme and vice versa. This may have been discussed in the literature but I am not sure. If so, it would probably be possible to adapt the Alice/Bob/Charlie story to…[Read more]

To be clear, there are two versions of protective measurement discussed in the literature. The “Zeno” version in which weak measurements are intersperesed with projective measurements, as discussed in Matt’s notes, and the adiabatic version referred to by Shan. For the adiabatic version, we do have a model of how a Gaussian state, e.g. the…[Read more]

Bob,

This is not to do with the status of the wavefunction specifically, but what I have always disliked about your approach to consistent histories is a consequence of the single framework rule.

Different frameworks may contain some projectors in common, which is precisely what happens in Bell-Kochen-Specker experiments. Any inferences between…[Read more]

Matt #1010,

Perhaps I can help Bob out by offering an example. It also happens in Spekkens’ toy theory. There, the set of pure states is isomorphic to the set of outcomes of maximally informative measurements. The former are epistemic and the latter represent ontic properties of the system.

Hi Ken,

“As a final note; the PBR theorem examines the status of the wavefunction at *preparation*, and determines it is ontic. And yet few people have examined models in which the wavefunction makes an ontic-to-epistemic transition (where the probability overlap between states grows with time).”

I don’t understand this comment. PBR employs…[Read more]

OK, yes that is roughly what I meant.

Shan, I should also comment that piping the audio from Skype into Google Hangouts, which is what I assume you are doing, does not work very well. Your audio is OK, but Valia and Richard were quite difficult to hear.

OK, since I have been outed as a lurker by Shan, let me ask how you would describe the role of the non-primitive ontology in a theory that does not support a division into states at a given time and dynamics? You previously suggested that the role of the non primitive ontology is to compute how the primitive ontology evolves in time, but what…[Read more]

Robert,

I think you are clearly a psi-epistemicist. For my purposes, this just means that you do not view the quantum state as an intrinsic property of an individual system. Whether you are neo-Copenhagen is a trickier question, which we have debated before over email. On my view, two key components of the Copenhagen interpretation are:

– The…[Read more]

Richard & Ken,

Perhaps the distinction between QBism and Richard’s position is similar to the difference between objective and subjective Bayesianism, or between the earlier “logical” theories of probability and subjective Bayesianism. In subjective Bayesianism, probabilities represent degrees of belief and they are not to be analysed into…[Read more]

Regarding this:

“This restricts such an agent’s access to information and so would make it necessary for him/her/it to aim for an ideal epistemic state that took account of all and only information about events in his/her/its backward light cone in forming beliefs about matters not so accessible.”

I wonder what your view of an object like “the w…[Read more]

I think there will be a lot of debate about the significance of protective measurements later in the workshop, so let’s perhaps put that to one side for now. I have a few comments more specific to Richard’s paper.

Firstly, I think it is a little bit unfortunate that the modern debate about the meaning of the wavefunction uses the terms “ontic”…[Read more]