The Preferred-Basis Problem and the Quantum Mechanics of Everything

Jereon Vink ([1993]) argued that there are two options for what he called a realistic solution to the quantum measurement problem: (1) select a preferred set of observables for which definite values are assumed to exist, or (2) attempt to assign definite values to all observables simultaneously (1810–1). While conventional wisdom has it that the second option is ruled out by the Kochen-Specker theorem, Vink nevertheless advocated it. Making every physical quantity determinate in quantum mechanics carries with it significant conceptual costs, but it also provides a way of addressing the preferred basis problem that arises if one chooses to pursue the first option. The potential costs and benefits of a formulation of quantum mechanics where every physical quantity is determinate are herein examined. 1 The preferred-basis problem 2 How to solve the preferred-basis problem 3 Relativistic constraints 4 Conclusion 1 The preferred-basis problem The standard unitary quantum dynamics and the standard interpretation of quantum mechanical states make it difficult to explain how observers end up with determinate measurement records. This is the quantum measurement problem. A direct solution to the quantum measurement problem would require one to find a formulation of quantum mechanics that (i) explains how observers end up with empirically accessible determinate measurement records, (ii) makes the standard quantum statistical predictions for these records, and (iii) is compatible with the constraints imposed by relativity. One might think of a solution to the quantum measurement problem as accomplishing (i) under the constraints of (ii) and (iii). # The Author (2005). Published by Oxford University Press on behalf of British Society for the Philosophy of Science. All rights reserved. doi:10.1093/bjps/axi114 For Permissions, please email: [email protected] In a formulation of quantum mechanics with only the unitary dynamics, an ideal measurement of a system S which is initially in a superposition of states Si corresponding to different determinate values qi of the quantity Q X