Concerning Wigner’s Former Roommate

I attended a workshop on the mini-genre of Extended Wigner’s Friend “paradoxes” but did not think that I’d write much on the topic myself. And, indeed, the comment I eventually produced is mostly bibliography.

B. C. Stacey, “On QBism and Assumption (Q)” [arXiv:1907.03805].

I correct two misapprehensions, one historical and one conceptual, in the recent literature on extensions of the Wigner’s Friend thought-experiment. Perhaps fittingly, both concern the accurate description of some quantum physicists’ beliefs by others.

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On Reconstructing the Quantum

It’s manifesto time! “Quantum Theory as Symmetry Broken by Vitality” [arXiv:1907.02432].

I summarize a research program that aims to reconstruct quantum theory from a fundamental physical principle that, while a quantum system has no intrinsic hidden variables, it can be understood using a reference measurement. This program reduces the physical question of why the quantum formalism is empirically successful to the mathematical question of why complete sets of equiangular lines appear to exist in complex vector spaces when they do not exist in real ones. My primary goal is to clarify motivations, rather than to present a closed book of numbered theorems, and consequently the discussion is more in the manner of a colloquium than a PRL.

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