Abstract:

Collective effects can significantly enhance the emission and absorption of light by an ensemble of two-level atoms. A well-known example is the so-called Dicke super-radiance occurring where excited atoms spontaneously emit light with an intensity scaling as the square of the number of atoms and a peaked angular distribution.

In our work, we focus instead on a regime where only a single excitation is stored collectively in the atoms. We study numerically the emission of such an excitation as a photon. It turns out that under suitable conditions, this photon may also be emitted with a peaked angular distribution and we calculate the exact spatio-temporal mode function for various arrangements of the atoms.

The phenomenon suggests realistic protocols for storing and retrieving a single photon from an atomic ensemble even without the use of a cavity, a task that is highly relevant for quantum information processing.