Rabi oscillations and excitation trapping in the coherent excitation of a mesoscopic frozen Rydberg gas

TL;DR

This paper demonstrates coherent Rydberg excitation in a mesoscopic ultracold atom ensemble, revealing interaction effects that include excitation trapping and enhanced excitation rates contrary to the dipole blockade.

Contribution

It introduces a novel excitation scheme with beam shaping and optical pumping, and explores interaction regimes showing unexpected excitation enhancement.

Findings

Observation of Rabi oscillations in a mesoscopic Rydberg gas

Detection of increased excitation rates at strong interactions

Contradiction of the dipole blockade effect in certain regimes

Abstract

We demonstrate the coherent excitation of a mesoscopic ensemble of about 100 ultracold atoms to Rydberg states by driving Rabi oscillations from the atomic ground state. We employ a dedicated beam shaping and optical pumping scheme to compensate for the small transition matrix element. We study the excitation in a weakly interacting regime and in the regime of strong interactions. When increasing the interaction strength by pair state resonances we observe an increased excitation rate through coupling to high angular momentum states. This effect is in contrast to the proposed and previously observed interaction-induced suppression of excitation, the so-called dipole blockade.