Quantum Behavior of Measurement Apparatus

TL;DR

This paper investigates the quantum properties of measurement apparatuses, introducing methods to analyze and experimentally characterize their quantum behavior, including projectivity, fidelity, and non-classicality, with applications to optical detectors.

Contribution

It provides a novel framework for studying the quantum behavior of measurement devices through pre-measurement states and proposes an experimental tomography procedure for optical detectors.

Findings

Quantum properties of measurement devices can be characterized via pre-measurement states.

The proposed tomography method enables experimental analysis of detector quantum behavior.

Application to optical detectors demonstrates the framework's practical relevance.

Abstract

We precise for the first time the quantum behavior of a measurement apparatus in the framework of the usual interpretation of quantum physics. We show how such a behavior can also be studied by the retrodiction of pre-measurement states corresponding to its responses. We translate in terms of these states some interesting properties of the behavior of an apparatus, such as the projectivity, the fidelity, the non-Gaussian character, or the non-classicality of measurements performed by this one. We also propose an experimental procedure allowing the tomography of these pre-measurement states for optical detectors. We illustrate the relevance of these new notions for measurements, by evaluating them for two detectors widely used in quantum optics: the avalanche photodiode and the homodyne detection.