Radiation trapping in a dense cold Rydberg gas

TL;DR

This paper explores how radiation trapping influences Rydberg excitation in cold gases, revealing new mechanisms and probing techniques, and discusses the interplay of multiple scattering and long-range interactions in quantum optics.

Contribution

It introduces radiation trapping as a new mechanism for Rydberg excitation and demonstrates its use as an in situ probe of scattered light properties.

Findings

Radiation trapping enhances Rydberg excitation in dense cold gases.

Rydberg excitation can mimic saturation effects similar to Rydberg blockade.

Multiple scattering and long-range interactions coexist, affecting quantum optics experiments.

Abstract

Cold atomic gases resonantly excited to Rydberg states can exhibit strong optical nonlinearity at the single photon level. We observe that in such samples radiation trapping leads to an additional mechanism for Rydberg excitation. Conversely we demonstrate that Rydberg excitation provides a novel in situ probe of the spectral, statistical, temporal and spatial properties of the trapped re-scattered light. We also show that absorption can lead to an excitation saturation that mimics the Rydberg blockade effect. Collective effects due to multiple scattering may co-exist with co-operative effects due to long-range interactions between the Rydberg atoms, adding a new dimension to quantum optics experiments with cold Rydberg gases.