Kanu Sinha: Superradiance, subradiance and superduperradiance: collective non-Markovian dynamics of atoms at long distances

Abstract: The interaction between a collection of atoms and light can be cooperatively modified via quantum correlations between the atoms. Such cooperative light-matter interaction can be understood as a constructive or destructive interference between the atomic dipoles and the emitted radiation, which manifests as an enhancement (superradiance) or suppression (subradiance) of the total spontaneous emission from the atomic ensemble. I will present an overview of collective atom-field interactions going from short interatomic separations to distances comparable to coherence length of the emitted photons, wherein the memory effects of the intermediary electromagnetic environment become pronounced. I will discuss how such a system can exhibit surprisingly rich non-Markovian dynamics, with collective spontaneous emission rates exceeding those of regular Dicke superradiance (‘superduperradiance’), formation of highly delocalized atom-photon bound states and spontaneous generation of atom-atom entanglement in the presence of delay. I will also discuss the advantages of such non-Markovian dynamics towards sensing field distributions. As a spatially varying field influences the atoms (e.g., by inducing a relative frequency detuning in the atomic transitions), we demonstrate that time-delayed feedback can enhance the quantum Fisher information associated with field gradient sensing. Our results present a new avenue for atom-based gradiometric sensors, utilizing non-Markovian features of the electromagnetic environment.