Subjective and Objective Probabilities in Quantum Mechanics

Mark Srednicki

Published 2005-01-03, updated 2005-01-14Version 2

We discuss how the apparently objective probabilities predicted by quantum mechanics can be treated in the framework of Bayesian probability theory, in which all probabilities are subjective. Our results are in accord with earlier work by Caves, Fuchs, and Schack, but our approach and emphasis are different. We also discuss the problem of choosing a noninformative prior for a density matrix.