Abstract
I discuss our experiments with optically levitated nanoparticles in ultrahigh vacuum. Using an active parametric feedback scheme we cool the particle’s center-of-mass temperature to T = 500 micro-Kelvins and reach mean quantum occupation numbers of n = 50. I show that mechanical quality factors of Q = 10^9 can be reached and that damping is dominated by photon recoil heating. The vacuum-trapped nanoparticle forms an ideal model system for studying nonequilibrium processes, nonlinear interactions, and ultrasmall forces.
