The limits of optical measurement are set by the quantum nature of light. The familiar shot noise limit can be avoided by increasing the optical power, but at high enough powers, the radiation pressure of the randomly-arriving photons can become the dominant force on the system, obscuring the signal that was to be measured. In this talk, I will discuss our experiment using light to cool the motion of a micromechanical membrane resonator to the quantum backaction limit, where the shot noise fluctuations of the light set a minimum temperature analogous to the Doppler limit of atomic laser cooling.
I will conclude with a discussion of a second experiment to couple microwave and optical frequency light using mechanical resonators. Our goal in this work is to create a device that could convert microwave quantum signals to optical frequencies, enabling long-distance quantum networks of microwave devices. I will outline our result where we convert classical signals at 10% photon number efficiency, and describe ongoing progress towards the quantum regime.
Host: Philip Walther