Detecting the degree of macroscopic quantumness using an overlap measurement

TL;DR

This paper explores experimental methods to measure macroscopic quantum superpositions using overlap measurements, analyzing their feasibility considering detection inefficiencies and coarse-graining effects.

Contribution

It proposes and evaluates schemes for detecting macroscopic quantumness in harmonic oscillator and qubit states, addressing practical experimental challenges.

Findings

Overlap measurement schemes are feasible with current technology.

Detection inefficiency impacts measurement accuracy but can be mitigated.

Coarse-graining effects are significant and must be carefully managed.

Abstract

We investigate how to experimentally detect a recently proposed measure to quantify macroscopic quantum superpositions [Phys. Rev. Lett. 106, 220401 (2011)], namely, "macroscopic quantumness" $\mathcal{I}$. Schemes based on overlap measurements for harmonic oscillator states and for qubit states are extensively investigated. Effects of detection inefficiency and coarse-graining are analyzed in order to assess feasibility of the schemes.