Collective strong coupling in multimode cavity QED

TL;DR

This paper demonstrates collective strong coupling in a multimode cavity QED system, showing mode-resolved resonances and mode coupling mediated by an atomic ensemble, with implications for quantum information and spin glass simulations.

Contribution

It provides the first experimental observation of collective strong coupling across multiple degenerate cavity modes and analyzes mode interactions mediated by atoms.

Findings

Well-resolved atom-cavity resonances for multiple modes

Cavity modes are coupled via the atomic ensemble

Supports quantum information processing and spin glass realization

Abstract

We study an atom-cavity system in which the cavity has several degenerate transverse modes. Mode-resolved cavity transmission spectroscopy reveals well-resolved atom-cavity resonances for several cavity modes, a signature of collective strong coupling for the different modes. Furthermore, the experiment shows that the cavity modes are coupled via the atomic ensemble contained in the cavity. The experimental observations are supported by a detailed theoretical analysis. The work paves the way to the use of interacting degenerate modes in cavity-based quantum information processing, where qubits corresponding to different cavity modes interact via an atom shared by the two modes. Our results are also relevant to the experimental realization of quantum spin glasses with ultracold atoms.