Lumped-Element Josephson Junction Array Resonators for Rapid Fabrication Characterization

Josephson junctions are the key element of all superconducting quantum circuits. With the development of more advanced quantum processors based on e.g. fluxoniums, Josephson junction arrays play an increasingly important role, and circuit performance becomes even more sensitive to junction quality and yield than in transmon-based processors. We present a compact lumped-element Josephson junction array resonator design that enables rapid extraction of junction parameters directly from transmission measurements. From the resonance frequency of the LC circuit and the plasma frequency of the array, the critical current density can be determined. The internal quality factor, in turn, provides information on dielectric and conductive losses and serves as a quantitative metric for process optimization. Multiple resonators can be coupled to a common feed line, enabling simultaneous measurement of a large number of junction arrays and providing statistical insight from a single two-port sample. The devices can be characterized with standard VNA measurements, supporting high-throughput optimization of Josephson junction fabrication for scalable quantum processor development.