Quantum Circuits Using the Disordered Superconductor WSi (Part I)

Kinetic inductance materials have been widely used in the superconducting detector community and are now applied in circuit QED, allowing for the implementation of distributed high inductance and highly nonlinear elements. However, devices based on such materials have not yet reached the simultaneous levels of high nonlinearity and low loss commonly achieved with Josephson junction-based devices. In this project, we aim to address this problem by optimizing devices based on WSi, an amorphous superconductor commonly used in single-photon detectors for its lack of grain boundaries and high-quality thin films.

In part one of this three-part talk, we present measurements of lumped and distributed WSi resonators. In addition, we utilize WSi as the linear inductor in fluxonium, where the flux tunability is utilized to characterize the frequency dependence of inductive losses.