Non-Gaussian correlations in the steady-state of driven-dissipative clouds of two-level atoms

Abstract

We report experimental measurements of the second-order coherence function $g^{(2)}(\tau )$ of the light emitted by a laser-driven dense ensemble of ${}^{87}$Rb atoms. We observe a clear departure from the Siegert relation valid for Gaussian chaotic light. Measuring intensity and first-order coherence, we conclude that the violation is not due to the emergence of a coherent field. This indicates that the light obeys non-Gaussian statistics, stemming from non-Gaussian correlations in the atomic medium. More specifically, the steady-state of this driven-dissipative many-body system sustains high-order correlations in the absence of first-order coherence. These findings call for new theoretical and experimental explorations to uncover their origin and they open new perspectives for the realization of non-Gaussian states of light.

After running new experiments, we discovered that saturation effects of avalanche photodiodes caused a significant reduction of measured second-order coherence. As a consequence, while non-Gaussian correlations are not excluded, further experiments and simulations are needed to support the claim of the manuscript