Linking Measures for Macroscopic Quantum States via Photon-Spin Mapping

TL;DR

This paper compares various measures of macroscopic quantumness in photonic and spin systems using a model that maps photonic states to spin ensembles, revealing strengths and limitations of these measures.

Contribution

It provides a comparative analysis of different measures for macroscopic quantum states through a photon-spin mapping model, highlighting their similarities and issues.

Findings

Some spin measures struggle with photonic states considered macroscopically quantum

Certain measures show significant similarities despite different motivations

The model reveals limitations and compatibilities among measures

Abstract

We review and compare several measures that identify quantum states that are "macroscopically quantum". These measures were initially formulated either for photonic systems or spin ensembles. Here, we compare them through a simple model which maps photonic states to spin ensembles. On the one hand, we reveal problems for some spin measures to handle correctly photonic states that typically are considered to be macroscopically quantum. On the other hand, we find significant similarities between other measures even though they were differently motivated.