F\"orster interaction induced phase shift in a pair state interferometer

TL;DR

This paper reports on experiments demonstrating how F"orster resonances induce a tunable, dispersive phase shift in Rydberg atom pair states, revealing coherent control of interactions with implications for quantum information processing.

Contribution

It introduces a pair state interferometer to measure interaction-induced phase shifts and shows coherent control of F"orster resonances despite dephasing effects.

Findings

Dispersive phase shift observed around F"orster resonance

Interaction strength and sign can be tuned coherently

Coherent dynamics observed with pulsed F"orster coupling

Abstract

We present experiments measuring an interaction induced phase shift of Rydberg atoms at Stark tuned F\"orster resonances. The phase shift features a dispersive shape around the resonance, showing that the interaction strength and sign can be tuned coherently. We use a pair state interferometer to measure the phase shift. Although the coupling between pair states is coherent on the time scale of the experiment, a loss of visibility occurs as a pair state interferometer involves three simultaneously interfering paths and only one of them is phase shifted by the mutual interaction. Despite additional dephasing mechanisms a pulsed F\"orster coupling sequence allows to observe coherent dynamics around the F\"orster resonance.