Towards counting microwave photons at room temperature

A microwave photon counter can be based on upconversion of the microwave radiation to the optical domain, followed by the optical photon counting. The former process sets the detection bandwidth, the latter sets the time resolution sufficient for sub-THz photon counting at room temperature. We report our progress in developing an efficient and intrinsically noiseless microwaves-to-optics converter, which is based on a high-Q whispering gallery resonator with quadratic nonlinearity.