Observation of vacuum-induced collective quantum beats

TL;DR

This paper reports the experimental observation of vacuum-induced collective quantum beats in a three-level atomic system, demonstrating superradiant decay and vacuum-induced coupling effects in a dilute atomic gas.

Contribution

It provides the first experimental demonstration of quantum beats caused by vacuum-induced coupling between excited states in atoms initially prepared in a single excited level.

Findings

Observation of superradiant decay rates

Detection of collectively enhanced quantum beats

First experimental evidence of vacuum-induced coupling effects

Abstract

We demonstrate collectively enhanced vacuum-induced quantum beat dynamics from a three-level V-type atomic system. Exciting a dilute atomic gas of magneto-optically trapped $^{85}$Rb atoms with a weak drive resonant on one of the transitions, we observe the forward-scattered field after a sudden shut-off of the laser. The subsequent radiative dynamics, measured for various optical depths of the atomic cloud, exhibits superradiant decay rates, as well as collectively enhanced quantum beats. Our work is also the first experimental illustration of quantum beats arising from atoms initially prepared in a single excited level as a result of the vacuum-induced coupling between excited levels.