SiGe/Si-Based Electro-Optic Platform for Microwave-Optical Transduction
Superconducting qubit quantum computers offer new capabilities for quantum information processing, but require < 50 mK environments and near complete isolation from outside noise sources. To enable quantum information to be exchanged with these systems outside of cryogenic conditions by means of higher energy photons, many approaches towards microwaveoptical transduction are being explored by the research community. Three-wave mixing in linear electro-optic materials is a particularly appealing approach due to the inherent simplicity and elimination of excess noise sources that are introduced by intermediate states present in many alternative technologies. However, material microwave and optical loss rates have limited conversion efficiency below 50% in demonstrations to date. Here, I present IBM’s work towards integrating low loss SiGe/Si optical resonators with the low loss Nb-on-Si microwave resonators that have been developed for superconducting qubits. An effective linear electro-optic coefficient for coupling the microwave and optical fields by three wave mixing is induced by strongly biasing the microwave resonators to leverage the DC Kerr effect in Si and SiGe. For 1 MHz-rate transducers, the resulting microwave-optical coupling strength is calculated to be sufficient to reach the peak conversion efficiency condition. Demonstrating microwave-optical transduction in this platform is then dependent on achieving low defectivity fabrication of the proposed SiGe/Si optical waveguides. I will present a study of this materials problem and an analysis of the overall optimal transducer design. This work was funded by LPS/ARO under CQTS program, contract number W911NF-18-1-0022.