Vacuum-stimulated cooling of single atoms in three dimensions

Controlling quantum dynamical processes is the key to practical applications of quantum physics, for example in quantum information science. The manipulation of light-matter interactions at the single-atom and single-photon level can be achieved in cavity quantum electrodynamics, in particular in the regime of strong coupling in which atom and cavity form a single entity. In the optical domain, this requires a single atom at rest inside a microcavity. Here we show that an orthogonal arrangement of a cooling laser, trapping laser and cavity vacuum gives rise to a unique combination of friction forces that act along all three directions. This combination of cooling forces is applied to catch and cool a single atom in a high-finesse cavity. The high cooling efficiency leads to a low temperature and an average single-atom trapping time of 17 s, during which the strongly coupled atom can be observed continuously.