  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.
