ABSTRACT
In this chapter we will explore some directions in the study of optomechanical systems that incorporate additional quantum degrees of freedom, beyond the cavity field and a mechanical resonator. A typical example includes a single two-level system coupled, either, to the field, the mechanics, or both. We will, further, introduce optomechanical systems within which the mechanical resonator is simultaneously coupled to both an optical cavity and a microwave resonator. In other examples not considered in detail here, the optomechanical system can be coupled to a gas of cold atoms, for example, a Bose-Einstein condensate [285, 266, 56, 186, 146, 30], or a superfluid [84, 135, 5].
