
Matthew Pusey joined the group 2018 Workshop on Wigner’s Friend 1 year, 11 months ago


Matthew Pusey replied to the topic Are there really two different Bell’s theorems? in the forum John Bell Workshop 2014 5 years, 8 months ago
Hi Howard,
I agree with your first paragraph.
“Local determinism” (LD) indeed encompasses everything you need for the 1964 Bell’s theorem [minimal]. I was attempting to reserve DL just for the formulation of locality once determinism is already in place. I think it makes phrases like “any reasonable “localist” notion that manifestly reduc…[Read more]

Matthew Pusey replied to the topic Are there really two different Bell’s theorems? in the forum John Bell Workshop 2014 5 years, 8 months ago
Hi all,
I can’t help wondering if a few tweaks to Howard’s nomenclature might help bridge much of the remaining divide. How about something like this:
Deterministic Locality (DL): A somewhat clunky name for Travis’ equation 3.
A 1964 Bell’s theorem: any theorem of the form “There exist quantum phenomena for which there is no theory satisfying…[Read more] 
Matthew Pusey replied to the topic Are there really two different Bell’s theorems? in the forum John Bell Workshop 2014 5 years, 8 months ago
Howard #1872,
Of course nobody would have put it quite like I did in 1964. But the DAG is an attempt to formalise fairly natural and longstanding way of thinking about causality (as evidence: two different formulations based on functions and probabilities respectively, turn out to be completely equivalent), the basic ideas of which (e.g.…[Read more]

Matthew Pusey replied to the topic Are there really two different Bell’s theorems? in the forum John Bell Workshop 2014 5 years, 8 months ago
Hi Howard,
I can’t deny that the “operationalist” in me jumps to the parameter independence conclusion when reading any of your four quotations. Indeed that is why I didn’t question your interpretation until I read Travis’ paper. But, outside of the deterministic case, that interpretation requires a certain style of thinking about causation in…[Read more]

Matthew Pusey replied to the topic Are there really two different Bell’s theorems? in the forum John Bell Workshop 2014 5 years, 8 months ago
Hi Travis,
I guess B’ was (and still is) usually what drives people to B, so that “refuting” B’ certainly undermines the case for B, which I think is what Einstein was getting at in your quote.
Of course I agree that the EPR paper contains a valid argument from their background assumptions + perfect correlations to determinism, and that Bell…[Read more]

Matthew Pusey replied to the topic Are there really two different Bell’s theorems? in the forum John Bell Workshop 2014 5 years, 8 months ago
Travis,
I agree that Bell was probably taking the Einstein quote to be the definition of locality, and that it is stronger than your equation (3), as it applies to any “real factual situations”, not just predetermined measurement outcomes. However, to my mind the quote is not totally unambiguous in all cases (particularly when probabilities are…[Read more]

Matthew Pusey replied to the topic Are there really two different Bell’s theorems? in the forum John Bell Workshop 2014 5 years, 8 months ago
Hi Travis,
This is a belated comment to say thanks for your thoughtprovoking paper.
In particular, you paper has changed my mind on one point: it is wrong to say, as Howard did, that the theorem Bell proved in 1964 uses [what is now often called] parameter independence. Bell’s locality assumption is more accurately captured by your equation 3,…[Read more]

Matthew Pusey joined the group John Bell Workshop 2014 5 years, 9 months ago

Matthew Pusey replied to the topic Panel Discussion: How to make sense of the wave function? [Friday, EDT (UTC4): 3pm5pm] in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
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 psiontic interpretation, it seems unlikely to make sense of the wavefunction if that means provide natural explanations for it’s key properties (living in configuration space, collapse, etc).
Do we…

Matthew Pusey replied to the topic A PBRlike argument for psiontology in terms of protective measurements in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
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]

Matthew Pusey replied to the topic A PBRlike argument for psiontology in terms of protective measurements in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
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]

Matthew Pusey replied to the topic Why protective measurement does not establish the reality of the wave function in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
[Duplicate post was here]

Matthew Pusey replied to the topic Why protective measurement does not establish the reality of the wave function in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
Shan #1089,
Getting inaccurate expectation values is something that may or may not happen to Bob. Charlie just sits there doing projective measurements in a fixed basis over and over again, right?
Regards,
Matt 
Matthew Pusey replied to the topic A PBRlike argument for psiontology in terms of protective measurements in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
Hi Shan,
As the other Matt has already mentioned, the existence of psiepistemic models of protective measurement makes your argument difficult to swallow. But let me focus here on two more specific questions here:
1) Why couldn’t somebody also run your argument using the tomographyofprotector then projective measurementofsystem scheme?
2)…[Read more]

Matthew Pusey replied to the topic Why protective measurement does not establish the reality of the wave function in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
Ken #1081,
The best toy model for thinking about weak measurements is the Gaussian theory, because then you already have continuous variables to act as your pointer, the pointer can be prepared in a Gaussian state, and the “vonNeumann measurement” interaction is present in the theory.
A nice example for imaginary weak values is to prepare the…[Read more]

Matthew Pusey replied to the topic Why protective measurement does not establish the reality of the wave function in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
Ken #1074,
I’m afraid I don’t quite get your question. Which contexts are you talking about?
Cheers,
Matt 
Matthew Pusey replied to the topic Why protective measurement does not establish the reality of the wave function in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
Shan #1070,
We definitely need to think more about which schemes are or are not equivalent to the original ones. (There is also a question of what equivalence means exactly – for example if one scheme requires classical postprocessing of the data whilst another does the same processing “as it goes along”, does that necessarily mean they are not…[Read more]

Matthew Pusey replied to the topic Why protective measurement does not establish the reality of the wave function in the forum First iWorkshop on the Meaning of the Wave Function 5 years, 11 months ago
Shan #1053,
What we do or don’t know has no bearing on which POVMs exist. Of course it may affect our choice of POVM – if we already know what basis the system was prepared in, we can measure it in that basis and determine the correct state. I don’t think anybody would argue that this establishes the reality of the wavefunction. The claim is…[Read more]
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