A Bayesian account of quantum histories

Adrian Kent

Thomas Marlow

Blake C. Stacey

The interpretation of quantum mechanics known as QBism developed out of efforts to understand the probabilities arising in quantum physics as Bayesian in character. But this development was neither easy nor without casualties. Many ideas voiced, and even committed to print, during earlier stages of Quantum Bayesianism turn out to be quite fallacious when seen from the vantage point of QBism. I trace the history of what we might call “proto-QBism” becoming QBism proper, showing that the process was one of becoming consistently Jamesian. But William James and phenomenology are evolutionary cousins, and so guided by QBism's history, I will sketch ways in which phenomenological turns may be inspirational for future developments in the QBist project. The prize, I will argue, would be if phenomenology can evoke a new technical development in the reconstruction of quantum theory or the understanding of the classical limit.

S. Sýkora

Marcelo Losada, Roberto Laura

Thomas Marlow

We introduce a novel notion of probability within quantum history theories and give a Gleasonesque proof for these assignments. This involves introducing a tentative novel axiom of probability. We also discuss how we are to interpret these generalized probabilities as partially ordered notions of preference, and we introduce a tentative generalized notion of Shannon entropy. A Bayesian approach to probability theory is adopted throughout; thus the axioms we use will be minimal criteria of rationality rather than ad hoc mathematical axioms.