Many-body theory of excitation dynamics in an ultracold Rydberg gas

TL;DR

This paper presents a theoretical framework for modeling excitation dynamics in ultracold Rydberg gases, simplifying complex quantum equations to rate equations, and predicts novel effects like antiblockade, aligning qualitatively with experimental observations.

Contribution

It introduces a rate-equation-based approach for large ultracold Rydberg gases, extending previous models and predicting new excitation phenomena such as antiblockade.

Findings

Qualitative agreement with experimental excitation blockade.

Prediction of antiblockade effect in Rydberg gases.

Analysis of sources of quantitative discrepancies.

Abstract

We develop a theoretical approach for the dynamics of Rydberg excitations in ultracold gases, with a realistically large number of atoms. We rely on the reduction of the single-atom Bloch equations to rate equations, which is possible under various experimentally relevant conditions. Here, we explicitly refer to a two-step excitation-scheme. We discuss the conditions under which our approach is valid by comparing the results with the solution of the exact quantum master equation for two interacting atoms. Concerning the emergence of an excitation blockade in a Rydberg gas, our results are in qualitative agreement with experiment. Possible sources of quantitative discrepancy are carefully examined. Based on the two-step excitation scheme, we predict the occurrence of an antiblockade effect and propose possible ways to detect this excitation enhancement experimentally in an optical lattice as well as in the gas phase.