Our article Hyperradiance from collective behavior of coherently driven atoms has been published as Optica 4, 779-785 (2017).
The collective behavior of ensembles of atoms has been studied in-depth since the seminal paper of Dicke [Phys. Rev. 93, 99 (1954)], where he demonstrated that a group of emitters in collective states is able to radiate with increased intensity and modified decay rates in particular directions, a phenomenon that he called superradiance. Here, we show that the fundamental setup of two atoms coupled to a single-mode cavity can distinctly exceed the free-space superradiant behavior, a phenomenon we call hyperradiance. The effect is accompanied by strong quantum fluctuations and surprisingly arises for atoms radiating out-of-phase, an alleged non-ideal condition where one expects subradiance. We are able to explain the onset of hyperradiance in a transparent way by a photon cascade taking place among manifolds of Dicke states with different photon numbers under particular out-of-phase coupling conditions. These theoretical results can be realized with current technology and should thus stimulate future experiments.