How many interpretations of QM do you speak?

[Sambuco]

To violate SI (NSD) there has to be a correlation between measurement settings and the hidden variables of the quantum system. If you don't invoke hidden variables (and we don't), then what is correlated with the measurement settings to violate SI?

In these extended Wigner's friend scenarios, that role is played by the outcomes of the measurements performed by the friends located inside the laboratories. This is stated explicitly in Bong's paper:

"Within the definitions of L and NSD, c, d play the formal role of the hidden variables λ in the usual derivation of Bell inequalities. However, we emphasize again that those correspond to observed events, and note that we make no assumption about hidden variables predetermining all measurement outcomes."

In that excerpt, c, d are the results of the measurements made by Charlie and Debbie, respectively. They are Alice and Bob's friends.

By L we mean "no spooky actions at a distance," i.e., no superluminal influence acting between the wings of the experiment. That is causal by definition. Perhaps you also include separability in L?

No, L is simply the locality assumption in Bell's original formulation (1964). This does not include non-separability. From Bong's paper:

"The probability of an observable event e is unchanged by conditioning on a space-like-separated free
choice z, even if it is already conditioned on other events not in the future light-cone of z."

Lucas.

 

[Sambuco]

Then again I guess there’s a reason why it isn’t more populær.

I think it is because, ultimately, it is not really an "interpretation," since it proposes that the evolution is non-unitary as a consequence of limitations in measuring time with real clocks.

Lucas.

 

[Matterwave]

Regardless of how successfully it does so, I believe the article aims to formulate the measurement problem in a way that is: (i) clearer than current formulations, by avoiding the introduction of the notion of measurement, and (ii) allows for a more fruitful dialogue between different interpretations/schools.

Lucas.

Ok, I will add the paper to my reading list! It just keeps getting longer~

 

[sbrothy]

I think it is because, ultimately, it is not really an "interpretation," since it proposes that the evolution is non-unitary as a consequence of limitations in measuring time with real clocks.

Lucas.

That may well be the reason why I have difficulty regarding it as an “interpretation”.

 

[iste]

I would call it non-probabilistic.

By the way, a joint probability of position and momentum can be defined with the Husimi distribution. It satisfies all the Kolmogorov axioms. But the resulting marginal probability of position or momentum is not equal to the usual quantum mechanical probability of position or momentum, because this corresponds to a different type of measurement. The Husimi distribution is measured by a POVM measurement, which is not a projective measurement.

I think I change my mind, thinking about it; I think more assumptions and interpretation of what the probabilities are or are not about is needed to say they violate Kolmogorovan probability axioms. But they look like they do at face-value.

 

[Demystifier]

I think quantum theory is not so difficult to understand once you accept this: Quantum theory, in its usual textbook form, is not about the microscopic world itself. It is about the response of our macroscopic probes of the microscopic world. But it turns out that this response does not depend on details of the macroscopic probes, creating an illusion that the probes are not really important and that quantum theory is about the microscopic world itself, which creates a lot of confusion and apparent paradoxes.

 

[A. Neumaier]

Regardless of how successfully it does so, I believe the article aims to formulate the measurement problem in a way that is: (i) clearer than current formulations, by avoiding the introduction of the notion of measurement, and (ii) allows for a more fruitful dialogue between different interpretations/schools.

The best paper that formulates the measurement problem in a way that is clearer than current formulations is

• Muller, F. A. (2023). Six measurement problems of quantum mechanics. In Non-reflexive logics, non-individuals, and the philosophy of quantum mechanics: Essays in honour of the philosophy of Décio Krause (pp. 225-259). Cham: Springer International Publishing. https://arxiv.org/pdf/2305.10206

 

[sbrothy]

That may well be the reason why I have difficulty regarding it as an “interpretation”.

Six Measurements Problems of Quantum Mechanics.