title: Light-matter interaction in free space.
abstract: We review recent experimental advances in the field of efficient coupling of single atoms and light in free space. Furthermore, a comparison of efficient free space coupling and strong coupling in cavity quantum electrodynamics (QED) is given. Free space coupling does not allow for observing oscillatory exchange between the light field and the atom which is the characteristic feature of strong coupling in cavity QED. Like cavity QED, free space QED does, however, offer full switching of the light field, a 180° phase shift conditional on the presence of a single atom as well as 100% absorption probability of a single photon by a single atom. Furthermore, free space cavity QED comprises the interaction with a continuum of modes.
authors.affiliation: Institute of Optics, Information and Photonics, University of Erlangen-Nuremberg.
authors.forename: Gerd
authors.initials: G
authors.lastname: Leuchs
authors.forename: Markus
authors.initials: M
authors.lastname: Sondermann
keywords: atom-photon coupling; free space QED; strong focussing