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Quantum measurement problem

DOI: 10.4324/9780415249126-Q086-1
Version: v1,  Published online: 1998
Retrieved August 14, 2020, from

Article Summary

In classical mechanics a measurement process can be represented, in principle, as an interaction between two systems, a measuring instrument M and a measured system S, during which the classical states of M and S evolve dynamically, according to the equations of motion of the theory, in such a way that the ‘pointer’ or indicator quantity of M becomes correlated with the measured quantity of S. If a similar representation is attempted in quantum mechanics, it can be shown that, for certain initial quantum states of M and S, the interaction will result in a quantum state for the combined system in which neither the pointer quantity of M nor the measured quantity of S has a determinate value. On the orthodox interpretation of the theory, propositions assigning ranges of values to these quantities are neither true nor false. Since we require that the pointer readings of M are determinate after a measurement, and presumably also the values of the correlated S-quantities measured by M, it appears that the orthodox interpretation cannot accommodate the dynamical representation of measurement processes. The problem of how to do so is the quantum measurement problem.

Citing this article:
Bub, Jeffrey. Quantum measurement problem, 1998, doi:10.4324/9780415249126-Q086-1. Routledge Encyclopedia of Philosophy, Taylor and Francis,
Copyright © 1998-2020 Routledge.

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