Nonclassicality of coherent states: Entanglement of joint statistics

TL;DR

This paper demonstrates that even states traditionally viewed as classical-like exhibit nonclassical features through joint measurements revealing inseparable statistics, challenging classical interpretations.

Contribution

It introduces a method to identify nonclassicality in classical-like states via nonseparable joint measurement statistics.

Findings

SU(2) spin coherent states are nonclassical under joint measurements

Glauber coherent states show nonclassical joint statistics

Thermal states exhibit nonclassical correlations in joint measurements

Abstract

Simple joint measurements of pairs of observables reveal that states considered universally as classical-like, such as SU(2) spin coherent states, Glauber coherent states, and thermal states are actually nonclassical. We show that this holds because we can find a joint measurement the statistics of which is not separable. Eventually this may be extended to all states different from the maximally mixed state.