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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 9 years, 5 months ago
I’m also done for today, but I’ll keep on eye on this tomorrow in case there are further thoughts.
Thanks to everyone for the stimulating responses that I think will, in the true spirit of a workshop, lead to improvements in the paper whenever it finally appears!
Matt
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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 9 years, 5 months ago
Shan #1046,
The claims you refer to apply only when one considers the totality of Bob and Charlie’s actions as a measurement procedure on the system from Alice. (Imagine putting Bob and Charlie in a huge black box, that has an input for the quantum system and a classical output of Bob’s estimate of the state.)
Since an arbitrarily sequence of…[Read more]
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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 9 years, 5 months ago
Bob #1045,
You might be interested to know that your example is pretty much exactly what protective measurement amounts to when carried out within the Bartlett, Rudolph, Spekkens model.
Yours,
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 9 years, 5 months ago
Shan #1042,
We should be able to reach agreement at least on this narrow point: Thinking of the protection-by-measurement (aka Zeno) scheme, does the protection amount to repeated applications of the channel given by eq. (1) in my notes?
(How this compares to the protection in the Hamiltonian-based scheme is probably a question for another day.…[Read more]
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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 9 years, 5 months ago
Thinking on the spot now, is there actually any difference between a small time-slice of a von-Neumann type strong measurement and a weak measurement? Weak measurements are normally obtained by reducing the interaction strength, but wouldn’t interacting for a shorter time amount to exactly the same thing?
If there is no difference, then my…[Read more]
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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 9 years, 5 months ago
Hi Shan,
Having returned to one of the original papers, I can see that you’re right that my “recap” of protective measurement does not quite agree with the original scheme, in which the “protecting” measurements are done during Bob’s measurement rather than only between them. Perhaps I heard about this scheme elsewhere and somehow I confused it…[Read more]
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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 9 years, 5 months ago
Hi Bob,
Thanks for your comment. Just to be clear about something I didn’t make explicit in the notes, I’m certainly not trying to argue that protective measurement is incompatible with the reality of the wave-function, and indeed in interpretations in which the wave-function is (always or sometimes) real it may well be a perfectly good method…[Read more]
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Matthew Pusey replied to the topic The Quantum Wave Function as Property and as Pre-probability in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Thanks, I think that helps. It’s just occurred to me that a similar ‘coincidence of ontic and epistemic’ actually occurs in Spekkens’ toy theory: the pure states and pure effects are the same set (just as in quantum theory), and yet there is a fact of the matter about whether a given system will result in a given pure effect (or if you like,…[Read more]
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Matthew Pusey replied to the topic The Quantum Wave Function as Property and as Pre-probability in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Hi,
Thanks for the interesting remarks. Given that ontic and epistemic are fundamentally different categories, would you agree that, generally speaking, it would be surprising to find something ontic and something epistemic represented by the same mathematics?
If you do not agree: can you think of an example of this occurring outside of quantum…[Read more]
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Matthew Pusey started 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 9 years, 5 months ago
At Shan’s suggestion I have switched to a text-based talk, since they seem to be working better. The attached notes (no paper yet, sorry!) contain roughly what I intended to say. In short, the claim is that thinking carefully about the role of the protector in protective measurement, both operationally and in simple ontological toy models,…[Read more]
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Matthew Pusey replied to the topic Does Protective Measurement Bear on the Meaning of the Wave Function? in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Hi Max,
Without wanting to put words in anyone’s mouth, I took Shan’s second point to be that if we can establish the reality of the expectation value of an arbitrary observable, then we have established the reality of the expectation values of all observables, and the latter is (more than) sufficient to reconstruct the wave function.
Yours,
Matt -
Matthew Pusey changed their profile picture 9 years, 5 months ago
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Matthew Pusey replied to the topic The meaning of the wave function. in the forum First iWorkshop on the Meaning of the Wave Function 9 years, 5 months ago
Hi Richard,
Thanks for your comments so far, I think I now understand your position a bit better. Obviously I’m more than a little late to the party, and my question isn’t about the wave function per se, but if you get a chance to respond to the following at some point, I’d be interested in your thoughts.
You’ve said that “quantum theory does…[Read more]
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Matthew Pusey joined the group Meaning of the Wave Function 9 years, 6 months ago