Collective excitation of Rydberg-atom ensembles beyond the $\sqrt{N}$ enhancement

TL;DR

This paper demonstrates a regime where interactions in Rydberg-atom ensembles enhance excitation probabilities through many-body coherences, challenging the usual suppression expectation.

Contribution

It introduces a novel regime where collective interactions lead to excitation enhancement via multi-photon coherences, expanding understanding of Rydberg ensemble dynamics.

Findings

Enhanced Rydberg excitation fraction observed

Build-up of many-body coherences identified

Potential for experimental verification with current setups

Abstract

In an ensemble of laser-driven atoms involving strongly interacting Rydberg states, the excitation probability is usually strongly suppressed. In contrast, here we identify a regime in which the steady-state Rydberg excited fraction is enhanced by the interaction. This effect is associated with the build-up of many-body coherences, induced by coherent multi-photon excitations between collective states. The excitation enhancement should be observable under currently-existing experimental conditions, and may serve as a direct probe for the presence of coherent multi-photon dynamics involving collective quantum states.