The Meaning of Protective Measurements

TL;DR

Protective measurements enable the measurement of a single quantum system's properties, including the wavefunction, by employing a protection mechanism, and this paper clarifies their interpretation and addresses misconceptions.

Contribution

This paper analyzes protective measurements, arguing they measure the quantum state itself rather than the protective potential, clarifying misunderstandings and defending their significance.

Findings

Protective measurements can measure the quantum state of a single system.

They do not merely reveal the protective potential.

The paper clarifies misconceptions about protective measurements.

Abstract

Protective measurements, which we have introduced recently, allow to measure properties of the state of a single quantum system and even the Schr\"odinger wave itself. These measurements require a protection, sometimes due to an additional procedure and sometimes due to the potential of the system itself. The analysis of the protective measurements is presented and it is argued, contrary to recent claims, that they measure the quantum state and not the protective potential. Some other misunderstandings concerning our proposal are clarified.