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Why protective measurement establishes the reality of the wave function

Gao, Shan (2018) Why protective measurement establishes the reality of the wave function. [Preprint]

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Abstract

It has been debated whether protective measurement implies the reality of the wave function. In this paper, I present a new analysis of the relationship between protective measurement and the reality of the wave function. First, I briefly introduce protective measurements and the ontological models framework for them. Second, I give a simple proof of Hardy's theorem in terms of protective measurements. It shows that when assuming the ontic state of the protected system keeps unchanged during a protective measurement, the wave function must be real. Third, I analyze two suggested psi-epistemic models of a protective measurement, in which the ontic state of the system is affected by the measurement. It is shown that although these models can explain the appearance of expectation values of observables in a single measurement, their predictions about the variance of the result of a non-ideal protective measurement are different from those of quantum mechanics. Finally, I argue that no psi-epistemic models exist for an ideal protective measurement in the ontological models framework, and in order to account for the definite result of an ideal protective measurement, the wave function must be a property of the protected system, defined either at a precise instant or during an infinitesimal time interval around an instant. Moreover, this result can also be extended to the wave function of an unprotected system. This new proof of the reality of the wave function does not rely on auxiliary assumptions, and it may help settle the issue about the nature of the wave function.


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Item Type: Preprint
Creators:
CreatorsEmailORCID
Gao, Shansgao7319@uni.sydney.edu.au
Keywords: protective measurement; wave function; ontological models framework; Hardy's theorem; psi-epistemic models; auxiliary assumptions
Subjects: Specific Sciences > Physics > Quantum Mechanics
Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Depositing User: Prof. Shan Gao
Date Deposited: 26 Aug 2018 14:39
Last Modified: 26 Aug 2018 14:39
Item ID: 14977
Subjects: Specific Sciences > Physics > Quantum Mechanics
Specific Sciences > Physics > Statistical Mechanics/Thermodynamics
Date: 26 August 2018
URI: https://philsci-archive-dev.library.pitt.edu/id/eprint/14977

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