Why protective measurement does not establish the reality of the quantum state
arXiv:1509.08893 · doi:10.1007/s40509-017-0111-4
Abstract
"Protective measurement" refers to two related schemes for finding the expectation value of an observable without disturbing the state of a quantum system, given a single copy of the system that is subject to a "protecting" operation. There have been several claims that these schemes support interpreting the quantum state as an objective property of a single quantum system. Here we provide three counter-arguments, each of which we present in two versions tailored to the two different schemes. Our first argument shows that the same resources used in protective measurement can be used to reconstruct the quantum state in a different way via process tomography. Our second argument is based on exact analyses of special cases of protective measurement, and our final argument is to construct explicit "-epistemic" toy models for protective measurement, which strongly suggest that protective measurement does not imply the reality of the quantum state. The common theme of the three arguments is that almost all of the information comes from the "protection" operation rather than the quantum state of the system, and hence the schemes have no implications for the reality of the quantum state.
19 pages, 6 figures
References in corpus (8)
- An Introduction to QBism with an Application to the Locality of Quantum Mechanics
- Is the quantum state real? An extended review of -ontology theorems
- Anomalous Weak Values Are Proofs of Contextuality
- How the result of a single coin toss can turn out to be 100 heads
- Disturbance in weak measurements and the difference between quantum and classical weak values
- Communication complexity and the reality of the wave-function
- Weak values in a classical theory with an epistemic restriction
- An argument for psi-ontology in terms of protective measurements