  Cavity quantum electrodynamics (C-QED) effects, such as Rabi splitting, Rabi
oscillations and superradiance, have been demonstrated with nitrogen vacancy
center spins in diamond in microwave resonators at cryogenic temperature. In
this article we explore the possibility to realize strong collective coupling
and the resulting C-QED effects with ensembles of spins at room temperature.
Thermal excitation of the individual spins by the hot environment leads to
population of collective Dicke states with low symmetry and a reduced
collective spin-microwave field coupling. However, we show with simulations
that the thermal excitation can be compensated by spin-cooling via optical
pumping. The resulting population of Dicke states with higher symmetry implies
strong coupling with currently available high-quality resonators and enables
C-QED effects at room temperature with potential applications in quantum
sensing and quantum information processing.
