Strong interaction between light and a single trapped atom without a cavity

TL;DR

This paper demonstrates strong interaction between a focused light beam and a single trapped rubidium atom without using a cavity, challenging the common belief that cavities are necessary for efficient atom-light coupling.

Contribution

It presents the first direct extinction measurement showing substantial coupling between light and a single atom in free space without a cavity.

Findings

Achieved significant atom-light coupling in free space.

Demonstrated potential for quantum information processing without cavities.

Opened new avenues for atom-photon interaction experiments.

Abstract

Coupling of light to an atom at single quanta level with high probability is a building block for many quantum information processing protocols. It is commonly believed that efficient coupling is only achievable with the assistance of a cavity. Here, we report on an observation of substantial coupling between a light beam and a single $^{87}$Rb atom in a direct extinction measurement by focusing light to a small spot with a single lens. Our result opens a new perspective on processing quantum information carried by light using atoms, and is important to many ongoing experiments that require strong coupling of single photons to an atom in free space.