New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong?

New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong

by Allison Filice

A thought experiment has shaken up the world of quantum foundations, forcing physicists to clarify how various quantum interpretations (such as many-worlds and the Copenhagen interpretation) abandon seemingly sensible assumptions about reality.

“This thought experiment is a great lens through which to examine the differences of opinions between different camps on the interpretation of quantum theory,” Spekkens said. “I don’t think it’s really eliminated options that people were endorsing prior to the work, but it has clarified precisely what the different interpretational camps need to believe to avoid this contradiction. It has served to clarify people’s position on some of these issues.”

Given that theoreticians cannot tell the interpretations apart, experimentalists are thinking about how to implement the thought experiment, in the hope of further illuminating the problem. But it will be a formidable task, because the experiment makes some weird demands. For example, when Alice makes a special measurement on her friend and her lab, it puts everything, the friend’s brain included, into a superposition of states.

I don't think there's a way to really explain the [thought] experiment - which I'm still thinking about - in three [quoted] paragraphs...plus the images help.

Aaronson has some commentary that might also be useful:

I first encountered Frauchiger and Renner’s argument back in July, when Renner (who I’ve known for years, and who has many beautiful results in quantum information) presented it at a summer school in Boulder, CO where I was also lecturing.  I was sufficiently interested (or annoyed?) that I pulled an all-nighter working through the argument, then discussed it at lunch with Renner as well as John Preskill.  I enjoyed figuring out exactly where I get off Frauchiger and Renner’s train—since I do get off their train.  While I found their paper thought-provoking, I reject the contention that there’s any new problem with QM’s logical consistency: for reasons I’ll explain, I think there’s only the same quantum weirdness that (to put it mildly) we’ve known about for quite some time.

Potentially useful supplements:

1. This thought experiment follows from one proposed by Eugene Wigner:




2. There's mention of QBism, which is Chris Fuch's idea:

A Private View of Quantum Reality

Quantum theorist Christopher Fuchs explains how to solve the paradoxes of quantum mechanics. His price: physics gets personal.

New Quantum Paradox Clarifies Where Our Views of Reality Go Wrong

by Allison Filice

This is the same thought experiment that was discussed a bit here:
https://psiencequest.net/forums/thread-r...physicists

Aaronson has some commentary that might also be useful:

To the limited extent that I can follow the arguments, Aaronson's objection to the thought experiment seems close to Lubos Motl's objection, which I referred to in the other thread (though Aaronson is much more polite).

This blogger, Lubos Motl, seems to be making essentially the same criticism - that when the first of the two observers outside the boxes makes his observation, it affects the systems inside the boxes, and the authors are not allowing for that. He presents it as a crass, obvious error:
https://motls.blogspot.com/2018/09/frauc...stent.html