Control of the Purcell effect via unexcited atoms and exceptional points

Abstract

We examine the possible control of the celebrated Purcell effect in cavity quantum electrodynamics. We demonstrate that the presence of an unexcited atom can significantly alter the Purcell decay depending on the strength of coupling of the unexcited atom with the cavity mode though the excited atom has to be weakly coupled for it to be in the Purcell regime. This cooperative behavior is distinct from the nonradiative nature of the singlet state which is an entangled state of the two-atom system. We present a physical interpretation for inhibition as due to interference between two polariton channels of decay. For specific values of the parameters, we bring out a connection to exceptional points in the cavity QED system as the unexcited atom and cavity mode can produce a second-order exceptional point. We further show how two unexcited atoms can create a third-order exceptional point leading to inhibition of the Purcell effect. We also discuss the case when the Purcell effect can be enhanced.