“Exploring quantum limits to optical measurement with millimeter-scale drums.”

"The pursuit of increasingly sensitive interferometric measurement of mechanical motion has played an important role in the history of quantum optics. In a continuous position measurement, one must ultimately confront the effect of quantum measurement backaction. The requirement to balance measurement imprecision with backaction forces results in a lower bound on sensitivity, the ‘standard quantum limit’. Decades ago many ideas for avoiding this 'limit' were studied in the context of the ultimate sensitivity of gravitational wave detection. However, it has proven difficult to realize interferometers actually limited by quantum backaction, which physically stems from the shot noise of radiation pressure. In recent years, there has been considerable progress in manipulating low-mass, high-frequency, and mechanically-isolated objects with radiation pressure. In our group we have developed a cryogenically-compatible Fabry-Perot cavity incorporating a millimeter-scale silicon-nitride membrane. In this talk, I present work in which we subject the membrane to a strong continuous position measurement and observe the shot noise of radiation pressure. Further, we demonstrate correlations between quantum fluctuations of the optical field and the mechanical motion and use these correlations to observe ponderomotive squeezing of light. Mechanical objects at quantum limits also hold promise for connecting disparate quantum resources, for example microwave and optical photons; I will describe initial work, in conjunction with Konrad Lehnert’s group at JILA, to combine our optomechanical device with an electromechanical interface. I will end with a brief update on our work to control motion at another scale, namely experiments with single neutral atoms in optical tweezers laser-cooled to their ground state."