Cavity Control and Cooling of Nanoparticles in High Vacuum

Levitated systems are a fascinating addition to the world of optically-controlled mechanical resonators. It is predicted that nanoparticles can be cooled to their c.o.m. ground state via the interaction with an optical cavity\footnote{T S Monteiro et al., \textbf{New J. Phys. 15} (2013)}. By freeing the oscillator from clamping forces dissipation and decoherence is greatly reduced, leading to the potential to produce long-lived, macroscopically spread, mechanical quantum states, allowing tests of collapse models and any mass limit of quantum physics. Reaching the low pressures required to cavity-cool to the ground state has proved challenging\footnote{\textbf{JM} et al., \textbf{Nature Nanotechnology 9}, 425 (2014)}. Our approach is to cavity cool a beam of nanoparticles in high vacuum. We can cool the c.o.m. motion of nanospheres\footnote{P Asenbaum, et al., \textbf{Nature Communications 4}, (2013)}, and control the rotation of nanorods\footnote{S Kuhn et al., \textbf{Nano Letters 15}, (2015)}, with the potential to produce cold, aligned nanostructures. Looking forward, we will utilize novel microcavities to enhance optomechanical cooling, preparing particles in a coherent beam ideally suited to ultra-high mass interferometry at $10^7$ a.m.u.