On the Aharonov-Anandan Experiment

TL;DR

The paper critically analyzes a proposed experiment claiming to measure non-commuting quantum observables without wave function collapse, arguing that it either involves wave function collapse or is not a true measurement, thus not resolving the wave function's reality.

Contribution

It provides a critical assessment showing that the proposed experiment cannot measure non-commuting observables without collapse or establish the wave function's reality.

Findings

The experiment either involves wave function collapse or is not a genuine measurement.

It does not demonstrate measurement of non-commuting observables without collapse.

It does not resolve the debate on the reality of the wave function.

Abstract

An experiment that would measure non--commuting quantum mechanical observables without collapsing the wave function has been recently proposed by Y Aharonov and J Anandan. These authors argue that this "protected measurement" may give indication on "the reality of the wave function". We argue that, depending of the precise version of the experiment considered, either the author's prediction is incorrect and the wave function does collapse, or the measurement is not a measurement on a quantum system. In either case, the experiment does not provide a way for measuring non--commuting observables without collapse, and it does not bear on the issue of the "reality of the wave function".