Non-Markovian spontaneous emission near an atomic quantum mirror

An ordered array of atoms in a Bragg configuration can behave as a mirror. We study an array of three-level atoms with two ground states |g> and |g’> coupled to a waveguide. We consider one of the ground states |g’> to be decoupled from the excited state, such that for the array atoms in |g’>, the collective system acts transparently towards incident electromagnetic field modes. Preparing the atomic array in a superposition of the two ground states, |g> and |g’> , puts it in a superposition of acting as a mirror or as a transparent boundary. Such systems are realizable in state-of-the-art experiments with Rydberg atom arrays and in circuit quantum electrodynamics (QED) where a coherent switching between different optical response has already been demonstrated.

We consider the interaction of such a “quantum mirror” with an excited two-level atom via the waveguide. We analyze the dynamics of the emitter and array as a function of various system parameters, such as the separation and detuning between the atomic emitter and the array and the number of atoms in the array. Considering large distances between the emitter and the array, we demonstrate time-delayed memory effects of the electromagnetic environment leading to non-Markovian dynamics of the collective atom-quantum mirror system.