Witnessing Optomechanical Entanglement with photon counting

The ability to coherently control mechanical systems with optical fields has made great strides over the past decade, and now includes the use of photon counting techniques to detect the non-classical nature of mechanical... [ view full abstract ]

The ability to coherently control mechanical systems with optical fields has made great strides over the past decade, and now includes the use of photon counting techniques to detect the non-classical nature of mechanical states. These ingredients may soon be used to perform an optomechanical Bell test, hence characterizing trustworthy optomechanical entanglement, i.e. independently of the details and imperfections of the actual implementation. Such a setup can also be used to implement a viable entanglement witness which avoids constraints on the global detection efficiencies; this is the witness we propose here. While our witness relies on a well-defined description and correct experimental calibration of the measurements, it does not require a detailed knowledge of the functioning of the optomechanical system. A feasibility study including dominant sources of noise and loss shows that it can readily be used to reveal optomechanical entanglement in present- day experiments with photonic crystal nanobeam resonators.