QBism: Quantum Theory as a Hero's Handbook

TL;DR

This paper elaborates on QBism, a subjective Bayesian interpretation of quantum mechanics, discussing its implications for quantum phenomena, cosmology, and foundational principles, with new insights and clarifications added to prior work.

Contribution

It provides an expanded and clarified exposition of QBism, integrating original material on quantum cosmology, SIC measurements, and the philosophical implications of quantum theory.

Findings

Quantum mechanics can be understood as a subjective Bayesian framework.

Bell inequality violations imply that nature is inherently creative.

SIC measurements are crucial for the technical development of QBism.

Abstract

This paper represents an elaboration of the lectures delivered by one of us (CAF) during "Course 197 -- Foundations of Quantum Physics" at the International School of Physics "Enrico Fermi" in Varenna, Italy, July 2016. Much of the material for it is drawn from arXiv:1003.5209, arXiv:1401.7254, and arXiv:1405.2390. However there are substantial additions of original material in Sections 4, 7, 8 and 9, along with clarifications and expansions of the older content throughout. Topics include the meaning of subjective probability; no-cloning, teleportation, and quantum tomography from the subjectivist Bayesian perspective; the message QBism receives from Bell inequality violations (namely, that nature is creative); the import of symmetric informationally complete (SIC) quantum measurements for the technical side of QBism; quantum cosmology QBist-style; and a potential meaning for the holographic principle within QBism.