Sub Cubic Millimeter Microwave Dielectric Resonators for Cavity Electro-Optic Transduction

We are building cavity electro-optic systems for coherent transduction between microwave and optical photons for quantum networks and for applications in quantum sensing. Our current system operates at room temperature in the triply resonant configuration (optical pump photons, microwave photons, and photons at the sum of those frequencies are all resonant with the electromagnetic modes of the structure) with high optical power handling. The all-dielectric microwave resonator consists of a LiNbO₃ crystal, with a sub-millimeter cross-section, sandwiched between high-k TiO₂ crystals creating boundaries of large dielectric contrast, thereby confining a high-Q, sub-mm³ mode inside the electro-optically active LiNbO₃. A Fabry-Perot optical cavity establishes a standing wave optical mode in the LiNbO₃. By carefully constructing and combining these particular microwave and optical modes we are able to achieve phase matched electro-optic conversion. Our near term goals are to establish quantum-calibrated sensing schemes for temperature metrology of microwave blackbody photons. Working towards a cryogenic regime, we would expect to achieve single-photon-level microwave to optical quantum transduction, facilitating coherent coupling between superconducting qubits and room-temperature fiber optic networks to enhance the efficiency and scalability of quantum communication technologies.