Observation of coherent coupling between super- and subradiant states of an ensemble of cold atoms collectively coupled to a single propagating optical mode

TL;DR

This paper demonstrates both theoretically and experimentally how an ensemble of cold atoms coupled to a single optical mode evolves through subradiant states, revealing collective quantum dynamics and power switch-offs.

Contribution

It provides the first experimental observation of the evolution through subradiant states in a cold atom ensemble coupled to a nanofiber, confirming theoretical predictions.

Findings

Observation of state evolution through subradiant states

Temporary suppression of emitted optical power

Agreement between theory and experimental results

Abstract

We discuss the evolution of the quantum state of an ensemble of atoms that are coupled via a single propagating optical mode. We theoretically show that the quantum state of N atoms, which are initially prepared in the timed Dicke state, evolves through all the N - 1 states that are subradiant with respect to the propagating mode. We predict this process to occur for any atom number and any atom-light coupling strength. These findings are supported by measurements performed with cold cesium atoms coupled to the evanescent field of an optical nanofiber. We experimentally observe the evolution of the state of the ensemble passing through the first two subradiant states, leading to sudden, temporary switch-offs of the optical power emitted into the nanofiber. Our results contribute to the fundamental understanding of collective atom-light interaction and apply to all physical systems, whose description involves timed Dicke states.