  Recently, remarkable advances have been made in coupling a number of high-Q
modes of nano-mechanical systems to high-finesse optical cavities, with the
goal of reaching regimes where quantum behavior can be observed and leveraged
toward new applications. To reach this regime, the coupling between these
systems and their thermal environments must be minimized. Here we propose a
novel approach to this problem, in which optically levitating a nano-mechanical
system can greatly reduce its thermal contact, while simultaneously eliminating
dissipation arising from clamping. Through the long coherence times allowed,
this approach potentially opens the door to ground-state cooling and coherent
manipulation of a single mesoscopic mechanical system or entanglement
generation between spatially separate systems, even in room temperature
environments. As an example, we show that these goals should be achievable when
the mechanical mode consists of the center-of-mass motion of a levitated
nanosphere.
