Theory for cavity cooling of levitated nanoparticles via coherent scattering: Master equation approach

We develop a theory for cavity cooling of the center-of-mass motion of a levitated nanoparticle through coherent scattering into an optical cavity. We analytically determine the full coupled Hamiltonian for the nanoparticle, cavity, and free electromagnetic field. By tracing out the latter, we obtain a master equation for the cavity and the center-of-mass motion, where the decoherence rates ascribed to recoil heating, gas pressure, and trap displacement noise are calculated explicitly. Then we benchmark our model by reproducing published experimental results for three-dimensional cooling. Finally, we use our model to demonstrate the possibility of ground-state cooling along each of the three motional axes. Our work illustrates the potential of cavity-assisted coherent scattering to reach the quantum regime of levitated nanomechanics.