Motional Signatures of Collective Spontaneous Emission. 

Ensembles of emitters coupled to the electromagnetic field can exhibit collective spontaneous emission via subradiance and superradiance. These systems are of interest because the emergent long lifetimes make them a promising platform for quantum memories and quantum metrology. In free space, interactions scale with the distance between emitters, thus, practical devices require inter-emitter spacing smaller than the transition wavelengths. While atoms or ions with longer transition wavelengths allow for collective modification with less stringent trapping requirements, they produce photons at frequencies that are hard to detect. We investigate the possibility of using residual motion as a readout to characterize collective emission. Most models treat emitters to be perfectly localized atoms, and those that do not generally consider motion to be a debilitating source of noise. However, evolution necessarily entangles the motional state and outgoing light due to recoil. We investigate whether the heating rate can reveal the lifetimes of collective states and how the motional correlations encode system's photon statistics.