Twin-beam-enhanced displacement measurement of a membrane in a cavity

We report an experimental demonstration of quantum-enhanced displacement measurement of a membrane in an optical cavity by using bright quantum correlated light to surpass the shot-noise limit (SNL). The optical cavity enhances the displacement signal and the twin beams suppress the noise background 3 dB below the SNL at an equivalent optical power. Thus, the signal-to-noise ratio is significantly improved by simultaneously using optical cavities and twin beams, and a sensitivity of 200 am/root Hz is achieved. The frequency fluctuations of twin beams are analyzed and reduced by using optical twin cavities. These results provide a useful method for precision measurements as well as to control cavity optomechanical systems with nonclassical light. Published under license by AIP Publishing.