Coupling a single trapped atom to a whispering-gallery-mode microresonator

TL;DR

This paper reports the successful trapping of a single rubidium atom near a whispering-gallery-mode microresonator and demonstrates strong coupling, enabling quantum applications leveraging chiral atom-light interactions.

Contribution

First demonstration of stable, controlled strong coupling between a single atom and a whispering-gallery-mode microresonator.

Findings

Observation of vacuum Rabi-splitting in the excitation spectrum

Successful compensation of trap-induced light shifts

Potential for quantum protocol implementation using chiral coupling

Abstract

We demonstrate trapping of a single 85Rb atom at a distance of 200 nm from the surface of a whispering-gallery-mode bottle microresonator. The atom is trapped in an optical potential, which is created by retroreflecting a red-detuned focused laser beam from the resonator surface. We counteract the trap-induced light shift of the atomic transition frequency by superposing a second laser beam with suitably chosen power and detuning. This allows us to observe a vacuum Rabi-splitting in the excitation spectrum of the coupled atom-resonator system. This first demonstration of stable and controlled interaction of a single atom with a whispering-gallery-mode in the strong coupling regime opens up the route towards the implementation of quantum protocols and applications that harvest the chiral atom-light coupling present in this class of resonators.