UC Berkeley

A cloud of ultracold atoms trapped within the confines of a high-finesse optical cavity shakes from the pressure of the light that probes it. This form of measurement backaction, a central component of quantum measurement theory, is the subject of this dissertation. Enlisting the collective motion of ultracold atoms as the mechanical degree of freedom in a cavity optomechanical system, we reach settings cold and quiet enough to allow for the effects of measurement backaction to manifest. We report predictions for and experimental observa- tions of the Standard Quantum Limit for force sensitivity, optical ponderomotive squeezing, and the possibility of complex squeezing through generalized optical correlations.