Cooling a Mechanical Resonator with a Nitrogen-Vacancy Center Ensemble   Using a Room Temperature Excited State Spin-Strain Interaction
  We propose a protocol to dissipatively cool a room temperature mechanical resonator using a nitrogen-vacancy (NV) center ensemble. The spin ensemble is coupled to the resonator through its orbitally-averaged excited state, which has a spin-strain interaction that has not been previously characterized. We experimentally demonstrate that the spin-strain coupling in the excited state is $13.5\pm0.5$ times stronger than the ground state spin-strain coupling. We then theoretically show that this interaction combined with a high-density spin ensemble enables the cooling of a mechanical resonator from room temperature to a fraction of its thermal phonon occupancy. 
E. R. MacQuarrie, M. Otten, S. K. Gray, and G. D. Fuchs
quant-ph cond-mat.mes-hall