  The search for experimental demonstrations of the quantum behavior of
macroscopic mechanical resonators is a fastly growing field of investigation
and recent results suggest that the generation of quantum states of resonators
with a mass at the microgram scale is within reach. In this chapter we give an
overview of two important topics within this research field: cooling to the
motional ground state, and the generation of entanglement involving mechanical,
optical and atomic degrees of freedom. We focus on optomechanical systems where
the resonator is coupled to one or more driven cavity modes by the radiation
pressure interaction. We show that robust stationary entanglement between the
mechanical resonator and the output fields of the cavity can be generated, and
that this entanglement can be transferred to atomic ensembles placed within the
cavity. These results show that optomechanical devices are interesting
candidates for the realization of quantum memories and interfaces for
continuous variable quantum communication networks.
