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 87Rb 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.
@article{arxiv.0802.3005,
title = {Strong interaction between light and a single trapped atom without a cavity},
author = {Meng Khoon Tey and Zilong Chen and Syed Abdullah Aljunid and Brenda Chng and Florian Huber and Gleb Maslennikov and Christian Kurtsiefer},
journal= {arXiv preprint arXiv:0802.3005},
year = {2009}
}