Noise and correlations in a microwave-mechanical-optical transducer*

Viewed as resources for quantum information processing, microwave and optical fields offer complementary strengths. We simultaneously couple one mode of a micromechanical oscillator to a resonant microwave circuit and a high-finesse optical cavity. In previous work, this system was operated as a classical converter between microwave and optical signals at 4 K, operating with 10\% efficiency and 1500 photons of added noise (1). To improve noise performance, we now operate the converter at 0.1 K. We have observed order-of-magnitude improvement in noise performance, and quantified effects from undesired interactions between the laser and superconducting circuit. Correlations between the microwave and optical fields have also been investigated, serving as a precursor to upcoming quantum operation. \\ \\ (1) Andrews, R. W., et. al. Bidirectional and efficient conversion between microwave and optical light. Nature Physics, \textbf{10}, 321–326 (2014).