Symmetry breaking and non-ergodicity in a driven-dissipative ensemble of multi-level atoms in a cavity

TL;DR

This study demonstrates a symmetry-breaking phase transition in a driven-dissipative multi-level atom-cavity system, revealing non-ergodic dynamics and potential applications in sensing and information processing.

Contribution

It reports the first observation of a $ ext{Z}_2$-symmetry-breaking transition with non-ergodic behavior in a multi-level atom-cavity system, highlighting new collective phenomena in dissipative quantum systems.

Findings

Observation of $ ext{Z}_2$-symmetry-breaking phase transition.

Emergence of multiple stationary states with disjoint basins.

Potential for sensing and pattern retrieval applications.

Abstract

Dissipative light-matter systems can display emergent collective behavior. Here, we report a $\mathbb{Z}_2$-symmetry-breaking phase transition in a system of multi-level $^{87}$Rb atoms strongly coupled to a weakly driven two-mode optical cavity. In the symmetry-broken phase, non-ergodic dynamics manifests in the emergence of multiple stationary states with disjoint basins of attraction. This feature enables the amplification of a small atomic population imbalance into a characteristic macroscopic cavity transmission signal. Our experiment does not only showcase strongly dissipative atom-cavity systems as platforms for probing non-trivial collective many-body phenomena, but also highlights their potential for hosting technological applications in the context of sensing, density classification, and pattern retrieval dynamics within associative memories.