Collective strong coupling in a lossy optical cavity

TL;DR

This paper demonstrates vacuum Rabi splitting in a lossy optical cavity through collective strong coupling, showing a clear $ ext{N}^{1/2}$ dependence despite weak single-atom coupling, with implications for quantum optics.

Contribution

It reports the observation of collective strong coupling in a lossy cavity, highlighting the $ ext{N}^{1/2}$ scaling of normal mode splitting with atom number, even with weak single-atom coupling.

Findings

Vacuum Rabi splitting observed in a lossy cavity.

Normal mode splitting scales as $ ext{N}^{1/2}$ with atom number.

Achieved coupling parameters with up to 1.33×10^5 cesium atoms.

Abstract

We observe vacuum Rabi splitting in a lossy nearly confocal cavity indicating the strong coupling regime, despite a weak single-atom single-mode coupling. Strong collective interaction manifests itself in the typical $\sqrt{N}$-dependence of the normal mode splitting on the number of atoms $N$. The $TEM_{00}$-mode coupling parameters are $(g,\kappa,\gamma)=2\pi\times(0.12,0.8,2.6)$ MHz and up to $(1.33\pm 0.08)\times10^5$ cesium atoms were loaded into the mode volume.