Cooling mechanical resonators to the quantum ground state from room temperature

Ground-state cooling ofmesoscopicmechanical resonators is a fundamental requirement for testing of quantum theory and for implementation of quantum information. We analyze the cavity optomechanical cooling limits in the intermediate coupling regime, where the light-enhanced optomechanical coupling strength is comparable with the cavity decay rate. It is found that in this regime the cooling breaks through the limits in both the strong-coupling and the weak-coupling regimes. The lowest cooling limit is derived analytically under the optimal conditions of cavity decay rate and coupling strength. In essence, cooling to the quantum ground state requires Q(m) > 2.4n(th), with Q(m) being the mechanical quality factor and n(th) being the thermal phonon number. Remarkably, ground-state cooling is achievable starting from room temperature, when the mechanical Q-frequency product Q(m)upsilon(m) > 1.5 x 10(13) Hz and both the cavity decay rate and the coupling strength exceed the thermal decoherence rate. Our study provides a general framework for optimizing the backaction cooling of mesoscopic mechanical resonators.