An excited atom will naturally decay to the ground state, with the exciting and emitted photons forming the basis for the optical protocols in quantum communication and computation. Within an ensemble of atoms, this emission process can proceed constructively, resulting in faster ensemble decay in an effect known as superradiance. In contrast to the superradiant process, Ferioli et al. report subradiance in an ensemble of excited rubidium atoms, where collective behavior between the decaying atoms proceeds destructively, thereby extending the lifetime of the excited atom ensemble in what can be described as a dark state. Engineering such dark states could provide a route to storing light. The reduced linewidth could also be useful in metrology applications.
Phys. Rev. X 11, 021031 (2021).