Current and proposed future gravitational wave detectors are expected to be broadly limited by quantum noise. This shows up as photon shot noise and radiation pressure noise due to quantum back-action. So far, the injection of squeezed vacuum into the detector has proven an effective way to reduce shot noise, further enhancing the detector’s astronomical reach.
In this talk, I will discuss an experiment done in collaboration with Louisiana State University (LSU) to measure broadband quantum radiation pressure at room temperature using a Gallium Arsenide (GaAs) micro-mirror. By injecting bright squeezed light into the optomechanical system, we have demonstrated the reduction of quantum radiation pressure noise at frequencies relevant for gravitational wave detectors at room temperature.
In order to achieve quantum noise reduction across the entire measurement band of the detector, a quadrature rotation of the injected squeezed state is required. This can be accomplished with a low-loss optical filter with bandwidth in the low-audio frequencies and remains a significant technical challenge. I will present an alternate method where frequency-dependent squeezing with Einstein-Podolsky-Rosen (EPR) entangled states is generated. When integrated into a gravitational wave detector, the method would eliminate the need for the low-loss optical filter.