# Single atoms coupled to a near-concentric cavity

## TL;DR

This paper demonstrates strong coupling between single rubidium atoms and a near-concentric optical cavity, achieving a coupling rate that surpasses atomic decay, which is promising for quantum information applications.

## Contribution

The study provides the first experimental realization of single-atom coupling in a near-concentric cavity with moderate finesse, showing strong atom-photon interaction without high finesse requirements.

## Key findings

- Achieved atom-cavity coupling constant g0=2π×5.0 MHz
- Coupling exceeds atomic decay rate γ by a factor of 1.7
- Demonstrated strong coupling in a 11mm long cavity

## Abstract

Concentric cavities can lead to strong photon-atom coupling without a need for high finesse or small physical-cavity volume. In a proof-of-principle experiment of this concept we demonstrate coupling of single Rb atoms to a 11mm long near-concentric cavity with a finesse F=138(2). Operating the cavity 1.65(1)$\mu$m shorter than the critical length, we observe an atom-cavity coupling constant $g_0=2\pi \times 5.0(2)\,$MHz which exceeds the natural dipole decay rate $\gamma$ by a factor $g_0/\gamma=1.7(1)$.