Erbium doped crystals for on-chip microwave to optical transduction

Microwave to optical transducers can enable the integration of superconducting quantum circuits in dilution refrigerators with room temperature optical communication networks. Ensembles of rare-earth ions (REIs) strongly coupled to microwave and optical resonators offer a promising platform for converting between microwave and optical photons at the quantum level. Among the REIs, erbium is particularly of interest due to its optical transitions within the telecom band.
Here, we present a REI-based transducer using a nanophotonic optical resonator and a superconducting lumped-element microwave resonator on an erbium-doped yttrium orthovanadate substrate. We achieve internal quality factors above 10,000 in both the optical and microwave domain, which is needed for efficient transduction. Initial characterization of the transducer at dilution temperatures will be presented.