Richard; but you would *lose* the common cause explanation of the gloves if you denied any ontology until the moment that the box was opened. A perfectly good explanation of a simple correlation would go missing, simply because you perhaps don’t want a similar (retrocausal) account in the Bell-violating case. And once you discard those prior…[Read more]

To Matt at #1128,

I agree.

To Ken at #1127,

I remain a retroskeptic, but keep trying!

The hand-waving response to the classically entangled gloves problem is to appeal to massive environmental decoherence of their state ensuring that each glove may be truly claimed to have its own classically developing trajectory since they were together. Then we get back a factorizable…[Read more]

Bob; maybe I can amplify Richard’s point in 1129… Those asking for a “QUANTUM” account all the way down are assuming that at bottom, the quantum description is the most fundamental. But in the psi-epistemic view (at least non-QBist versions of it), the quantum description is not fundamental at all.

A better way to frame your original…[Read more]

To Robert at #1126,

Would you agree with me that the measurement problem is, fundamentally, giving a fully QUANTUM description of the measurement process?

Not quite. The measurement problem is a consistency problem: to reconcile a quantum model of a unitary interaction that entangles wave functions of system and apparatus with the interpretative…[Read more]

How to make sense of the wave function?

I currently think the epistemic approach has the best hope of doing this. Even if one constructs a good psi-ontic interpretation, it seems unlikely to make sense of the wave-function if that means provide natural explanations for it’s key properties (living in configuration space, collapse, etc).

Do we…

[Read more]

Richard,

I agree that one *could* do this, but you’d end up with an impoverished ontology, for no particular gain (except perhaps a wider acceptance from people who don’t like retrocausality…? 🙂 )

Also, when it comes to entanglement, that approach wouldn’t shine any new light on what was going on. In the classical case that you have two…[Read more]

Dear Richard,

Relative to your #1122. I think for most of us ‘the wave function’ is something we can imagine arising from some sort of preparation: Alice has a device that produces a spin-half particle with S_x = 1/2, and we assign a wavefunction to the particle, and maybe also to the apparatus that produces it and to the measurement apparatus,…[Read more]

To Ken at #1123

For me, this just adds to the evidence that psi is best viewed as a collection of classical probability distributions, most of which are wrong. The correct distribution one should use is conditional on the future measurement geometry (i.e. the choice of the next strong measurement.) So psi is isomorphic to something like…

[Read more]

Dear Lee,

In response to your #1118, I confess I don’t know a great deal about the real ensemble formulation (REF), as I have only looked at it recently. As I understand it, there seems to be some resemblance to de Broglie-Bohm (dBB). I note that dBB suffers from a serious problem which was pointed out many years ago by Englert, Scully, Sussman…[Read more]

While I obviously don’t think psi is (always) ontic, I do feel that there are a lot of different perspectives that make psi seem more like an ordinary probability distribution than it normally does. These perspectives include many of the cases we’ve been talking about: protective measurements, consistent histories, weak measurements, and even to…[Read more]

Before asking for the meaning of the wave function shouldn’t we ask which wave function we are talking about?
Too often talk of “the wave function” seems to arise from the perspective of a quantum model without regard to its applications (to an entire toy universe? to an actual system in the lab.?)
For dBB, Everett and REF there is one “special”…[Read more]

Shan has posed several questions. Here are my answers

It is clear that wavefunctions are among the standard tools of textbook quantum mechanics, and nobody at this workshop has suggested that that is going to change. Furthermore, they are used to calculate or predict probabilities, and there are plenty of experimental data that agree with those…[Read more]

Shan #1115-#1117,

I’ve agreed that more work is required to clarify exactly what Bob’s strategy is in the original scheme and whether or not this is equivalent to my “recap”. Thanks for your additional ideas on this matter.

But as I have tried to make clear, the operational argument does not depend in any way on what the protective measurement…[Read more]

Max #1109,

I can tell you how I currently see this issue. As we’ve mentioned, the adiabatic scheme is present in the Gaussian toy theory. Recall that the ontology of that toy theory is just that of classical particle mechanics. This basically turns out to move the particle around in such a way that, for any observable allowed in the theory, the…[Read more]

Dear Shan,

I agree with you strongly. But deciding that the wavefunction is ontic, while very important, is of course not the end of the discussion, it is the beginning. It opens up the floor for us to propose hypotheses as to what beables the wave function corresponds to. Quantum mechanics doesn’t tell us, because of the measurement p…[Read more]

Here is my further idea (gotten on the bus to my office), which shows that there are more differences:

(1) The first one concerns the weak measurements (with readouts). These weak measurements result in strong wavefunction collapse. Here the strongness means that the probability to collapse most of the outcome states is large, although the…[Read more]

Dear Matt,

I must say that your scheme let me think more deeply about PM. I am very grateful to you for this.

I think we should not make assertions quickly; we need a more careful analysis and more effective discussions, especially because we have different opinions from the beginning.

Here is my current thoughts:

1. Your scheme is not the…[Read more]

Matt #1101:

Thanks for your further comments!

2) Are you saying the same protection can apply to two non-orthogonal states? Can you give an example of how that would work?

No, we need two different protections for two non-orthogonal states. The protection is taken as part of the state preparation procedure.

1) Why couldn’t somebody also run y…[Read more]

My answers to these questions are as follows:

1. We don’t need new experimental observations to understand the wave function. This is different from the case of the measurement problem. This is why I think we should first solve this problem.

2. Although we cannot exclude the anti-realist view, I believe we can find the true meaning of the wave…[Read more]