Uncover quantumness in the crossover from BEC to quantum-correlated phase

TL;DR

This paper investigates the quantum entanglement and statistical properties of a system of two-level emitters coupled to a cavity, revealing quantum correlations and departures from classical coherence across different regimes.

Contribution

It introduces a detailed analysis of quantum entanglement and statistical moments in the Tavis-Cummings model, highlighting quantum correlations beyond traditional phase transition studies.

Findings

Quantum entanglement varies across regimes.

Statistical moments reveal non-classical light and matter distributions.

Second order correlation function alone may not indicate coherence.

Abstract

Collective phenomena in the Tavis-Cummings model has been widely studied, focusing on the phase transition features. In many occasions, it has been used variational approaches that consider separated radiation-matters systems. In this paper, we examine the role of the quantum entanglement of an assembly of two-level emitters coupled to a single-mode cavity; this allows us to characterise the quantum correlated state for each regime. Statistical properties of the system, e.g., the first four statistical moments, show clearly the structure of the light and matter distributions. Even though the second order correlation function goes to one in some regimes, the statistical analysis evidence a sharp departure from coherent behaviour, contrarily to the common understanding.