We are developing high-efficiency microwave impedance transformers for microwave-to-optical quantum transducers. Our goal is to match a standard 50 Ω microwave environment to a novel high-impedance electro-optic (EO) device based on a 20-kΩ impedance traveling-wave modulator. The high impedance strengthens the microwave-to-optical interaction, enhances light–matter interaction inside the EO medium, and improves the overall transduction efficiency. We will use a Klopfenstein taper design as it provides low reflection with a compact length over a broad bandwidth. We target 4–8 GHz operation and near-unity coupling into 20-kΩ effective load impedances. We will implement the taper using NbTiN thin-film nanowire superconducting transmission lines. NbTiN is a strong material choice because it has a relatively high critical temperature for robust cryogenic operation, and high kinetic inductance for compact, high-impedance lines. By combining NbTiN high-kinetic-inductance lines with a Klopfenstein profile, this project aims to deliver a low-loss, broadband, and scalable microwave interface that boosts EO coupling and supports efficient microwave-to-optical quantum transduction.
Project is currently funded by: Federal