Controlled doping of a bosonic quantum gas with single neutral atoms

TL;DR

This paper demonstrates a method for precisely doping a Bose-Einstein condensate with individual neutral atoms, enabling advanced studies of impurity interactions in quantum gases.

Contribution

It introduces experimental techniques for controlled doping of a BEC with single neutral atoms, including cooling, localization, and transport methods.

Findings

Enhanced impurity immersion efficiency through Raman side-band cooling.

Localization of impurities in a species-selective optical lattice.

Monitoring of impurity-BEC interactions via three-body loss measurements.

Abstract

We report on the experimental doping of a $^{87}$Rubidium (Rb) Bose-Einstein condensate (BEC) with individual neutral $^{133}$Cesium (Cs) atoms. We discuss the experimental tools and procedures to facilitate Cs-Rb interaction. First, we use degenerate Raman side-band cooling of the impurities to enhance the immersion efficiency for the impurity in the quantum gas. We identify the immersed fraction of Cs impurities from the thermalization of Cs atoms upon impinging on a BEC, where elastic collisions lead to a localization of Cs atoms in the Rb cloud. Second, further enhancement of the immersion probability is obtained by localizing the Cs atoms in a species-selective optical lattice and subsequent transport into the Rb cloud. Here, impurity-BEC interaction is monitored by position and time resolved three-body loss of Cs impurities immersed into the BEC. This combination of experimental methods allows for the controlled doping of a BEC with neutral impurity atoms, paving the way to impurity aided probing and coherent impurity-quantum bath interaction.