Observation of Feshbach resonances between a single ion and ultracold atoms

TL;DR

This paper reports the first observation of Feshbach resonances between a single ion and ultracold atoms, enabling precise control of their interactions for quantum simulation and many-body physics.

Contribution

It demonstrates magnetically tunable Feshbach resonances in a hybrid atom-ion system, a significant advancement in controlling quantum interactions at ultracold temperatures.

Findings

Identification of Feshbach resonances between Ba+ ions and Li atoms

Enhanced three-body reactions at resonance points

Controlled ion sympathetic cooling in ultracold atomic bath

Abstract

Controlling physical systems and their dynamics on the level of individual quanta propels both fundamental science and quantum technologies. Trapped atomic and molecular systems, neutral and charged, are at the forefront of quantum science. Their extraordinary level of control is evidenced by numerous applications in quantum information processing and quantum metrology. Studying the long-range interactions between these systems when combined in a hybrid atom-ion trap has lead to landmark results. Reaching the ultracold regime, however, where quantum mechanics dominates the interaction, e.g., giving access to controllable scattering resonances, has been elusive so far. Here we demonstrate Feshbach resonances between ions and atoms, using magnetically tunable interactions between $^{138}$Ba$^{+}$ ions and $^{6}$Li atoms. We tune the experimental parameters to probe different interaction processes - first, enhancing three-body reactions and the related losses to identify the resonances, then making two-body interactions dominant to investigate the ion's sympathetic cooling in the ultracold atomic bath. Our results provide deeper insights into atom-ion interactions, giving access to complex many-body systems and applications in experimental quantum simulation.