Radiation pressure based lock-in amplifier for quantum metrology

A phase-sensitive amplifier could be useful for several quantum metrology applications, e.g. in future gravitational wave detectors to protect the injected squeezing against decoherence caused by readout losses. Such a fully coherent amplifier using opto-mechanics that operates beyond the Heisenberg limit could be realized in a traveling wave optical cavity with one or more mirrors also serving as the mechanical oscillator engineered with suitable susceptibility. Here, we describe a tabletop experiment to demonstrate such phase-sensitive amplification: the opto-mechanical nonlinearity is a gram-scale mirror on a cantilever which is in a triangular optical cavity with no detuning. We discuss, in particular, the noise budgeting and use of a Mach-Zehnder interferometer with two such cavities for a macroscopic quantum-limited tabletop experiment in the audio frequency band.