Efficient microwave-optical transduction using high overtone bulk acoustic resonances*

A device capable of converting single quanta of the microwave field to the optical domain is an outstanding endeavor in the context of quantum interconnects between distant superconducting qubits, but likewise can have applications in other fields, such as radio astronomy.     A variety of transduction approaches have been proposed and realized, yet none has attained the required vanishing added noises and an efficiency approaching unity. Here we present a new transduction scheme that could satisfy in theory the requirements for quantum coherent bidirectional transduction. Our scheme relies on an intermediary mechanical mode, a high overtone bulk acoustic resonance (HBAR), to couple coherently microwave and optical photons through the piezoelectric and strain-optical effects. The integration of MEMS actuators on the damascene silicon nitride photonic platform allows for very low loss and high power handling, essential for efficient conversion. We will present our theoretical understanding of this system, in particular the analysis of the conversion efficiency through signal flow graphs and the quantization of the piezoelectric interaction. Furthermore, we will expose preliminary experimental results with the first generation of these devices.