-
editor replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Hi Richard,
Thanks a lot for your further explanation! I now understand your third argument more clearly. I think the potential issue is that you used results from two different frames in the same inequality (32). Concretely speaking, I think in Alice’s frame corr(b, c) is not equal to E(b, c) = −cos(b − c). It seems that QM does not require thi…[Read more]
-
Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Thanks, Richard for this clarification.
Of course, I think your analysis can also perfectly well apply to an ontic role for the quantum state.
Under an epistemic view of the quantum state, then it seems to me that if one posits that measurements really do have definite outcomes, then an implicit hidden variable view must be lurking in the…[Read more] -
Richard Healey replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
The third argument makes no assumption of hidden variables. In particular, it makes no assumption concerning the actual spin values of the measured particles, either before or after the spin measurements. It assumes only that each measurement has a definite physical outcome, which may correspond to a light flashing red rather than green (for…[Read more]
-
editor replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Hi Richard,
Thanks for your kind explanation!
I understand that the inequality (31) is derived from the hidden variable assumption in Fine’s paper. But the statistical correlations between pairs of *actual experimental outcomes* does not necessarily satisfy the inequality. It is the assumption that these outcomes directly reflect the values of…[Read more]
-
Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
This is an interesting situation: assessments of the bearing and validity of the FR proof greatly depend on what quantum theory itself is taken to be. For example, Editor has referred to two different forms of QT:
(1) QT with collapse postulate — call it “QTCP”
(2) QT without collapse postulate — call it “QTNCP”
…and has noted, based on…[Read more] -
Richard Healey replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
As stated in the first sentence of the paragraph in which equation (31) appears, it is a central assumption of this third argument that every spin measurement performed by A,B,C and D has a definite, physical outcome. Consistent with that assumption, the measurements by A, B destroy all
- records
of C’s and D’s definite, physical outcomes. So none…[Read more]
-
editor replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Hi Richard,
I think there are two concerns about your third argument. The first is that in order to derive the Bell inequality (31), one needs a locality assumption for the factorization, e.g. of the term corr(c,d), which is the same as that in the original Bell inequality. The second concern is that in your thought experiment, it seems that the…[Read more]
-
Mark Stuckey joined the group 2018 Workshop on Wigner’s Friend 5 years, 5 months ago
-
Richard Healey replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Shan,
You say
” it seems to me that Richard’s result about the Limits of Objectivity is not valid. This result is derived from the third argument in his paper. I think the argument is based on the implicit assumption of locality, like Bell’s theorem, and one should drop this locality assumption, not the objectivity of outcomes.”Where do you thi…[Read more]
-
Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
I would just comment here that Brukner’s formulation of the measurement problem presupposes an epistemic interpretation of the quantum state relative to a particular observer. So his analysis and conclusions do not apply to cases in which the quantum state ontologically refers. In particular, he concludes that facts are necessarily…[Read more]
-
Aurelien Drezet replied to the topic Response to Frauchiger and Renner in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Dear Friends, I discovered the work by Frauchiger and Renner yesterday.
I didn’t read the literature on the topics but I wrote a kind of comment which I put on arxiv one hour ago. Being a Bohmian my view is that actually this is just a rephrasing of Hardy’s paradox involving nonlocality between agents. The problem is not more…[Read more] -
Aurelien Drezet posted an update in the group 2018 Workshop on Wigner’s Friend 5 years, 5 months ago
Dear Friends, I discovered the work by Frauchiger and Renner yesterday.
I didn’t read the literature on the topics but I wrote a kind of comment which I put on arxiv one hour ago. Being a Bohmian my view is that actually this is just a rephrasing of Hardy’s paradox involving nonlocality between agents. The problem is not more…[Read more] -
Aurelien Drezet joined the group 2018 Workshop on Wigner’s Friend 5 years, 5 months ago
-
Tony Sudbery started the topic On the second FR argument in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
On the second FR argument
The theorem claimed by Frauchiger and Renner in their recent publication in Nature Communications is different from the one they presented in their eprint arXiv:1604.07422, which was discussed in the references to this forum. Both theorems use the same extension of the Wigner’s friend experiment and claim to show that…[Read more]
-
Ruth Kastner started the topic How we avoid getting to the Wigner's Friend situation in the first place in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
The Wigner’s Friend scenario was created to amplify the measurement problem as illustrated by Schrodinger’s Cat. We don’t encounter a Wigner’s Friend dilemma in the first place if we have a means of delineating, in physical terms, what constitutes ‘measurement’ (where that is described by von Neumann’s Process 1 non-unitary transition)…[Read more]
-
editor replied to the topic Response to Frauchiger and Renner in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
A good paper, Dustin. Your analysis is consistent with the analyses of others, including those of Tony and Richard, which are listed in the “References related” post. Shan
-
editor replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Yes, Ruth. You may start a new topic to address the measurement problem.
-
editor replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Thanks for your comments, Nikolay.
-
Dustin Lazarovici started the topic Response to Frauchiger and Renner in the forum Workshop on Wigner’s Friend 2018 5 years, 5 months ago
Dear all,
thanks for the opportunity to participate. My colleague Mario Hubert and I have written a comment on the paper of Frauchiger and Renner (2018) “Quantum theory cannot consistently describe the use of itself”. We believe that their “no-go theorem” doesn’t actually show anything of interest. In particular, if the proposed thought…[Read more]
-
Ruth Kastner replied to the topic Is there an inconsistent friend? in the forum Workshop on Wigner’s Friend 2018 5 years, 6 months ago
Dear Editor: Should I start a new topic to address the measurement problem, which is what is being illustrated by the Wigner’s Friends scenario? In particular, we don’t encounter a Wigner’s Friend dilemma in the first place if we have a means of delineating, in physical terms, what constitutes ‘measurement’ (where that is described by von…[Read more]
- Load More