Storage enhanced nonlinearities in a cold atomic Rydberg ensemble

TL;DR

This paper demonstrates how storing optical pulses as Rydberg polaritons in a cold atomic ensemble enhances Rydberg-mediated interactions, revealing two distinct time-scale regimes and implications for quantum optics.

Contribution

It provides the first experimental demonstration of storage-enhanced Rydberg interactions and characterizes the dynamics over different storage times.

Findings

Strong interaction enhancement at short storage times

Observation of Rydberg dephasing at longer times

Non-linear dependence of coherence time on photon number

Abstract

The combination of electromagnetically induced transparency (EIT) with the nonlinear interaction between Rydberg atoms provides an effective interaction between photons. In this paper, we investigate the storage of optical pulses as collective Rydberg atomic excitations in a cold atomic ensemble. By measuring the dynamics of the stored Rydberg polaritons, we experimentally demonstrate that storing a probe pulse as Rydberg polaritons strongly enhances the Rydberg mediated interaction compared to the slow propagation case. We show that the process is characterized by two time scales. At short storage times, we observe a strong enhancement of the interaction due to the reduction of the Rydberg polariton group velocity down to zero. For longer storage times, we observe a further, weaker enhancement dominated by Rydberg induced dephasing of the multiparticle components of the state. In this regime, we observe a non-linear dependence of the Rydberg polariton coherence time with the input photon number. Our results have direct consequences in Rydberg quantum optics and enable the test of new theories of strongly interacting Rydberg systems.