In the 1970's, during the theoretical investigation of the ultimate sensitivity of gravitational wave detectors, it was understood that quantum fluctuations of the electro-magnetic field used to probe the motion, would produces a force noise which would limit the sensitivity. After this was understood, people developed schemes to avoid this limitation by giving up complete knowledge of the motion. In our recent experiments with micron-scale mechanical structures coupled to microwave resonators at milli-kelvin temperatures, we detect this force noise generated by the quantum fluctuations of a microwave field, and show how to avoid this stochastic noise by measuring a single quadrature of motion. I will also discuss our recent work with superfluid helium which we hope will demonstrate the wavelike nature of a centimeter/gram scale object.

Argonne Physics Division Colloquium Schedule