Abstract

Superconducting quantum circuits have made impressive advances, yet face core limitations that hinder coherence, reproducibility, and scalability. Chief among these are decoherence from two-level systems (TLS), the variability of amorphous tunnel barriers, and constraints from low-gap superconductors like aluminum. In this talk, I will present our group’s efforts to overcome these challenges by developing a fully niobium-based fabrication process featuring in-situ trilayer Nb/AlO_x/Nb junctions. This approach yields cleaner interfaces, improved junction uniformity, and enables operation at higher frequencies and temperatures thanks to niobium’s larger superconducting gap. These advances directly address the limitations imposed by the low cooling power available at millikelvin temperatures—typically just a few hundred microwatts at 100 mK—by allowing qubit operation closer to 1 K and reducing thermal sensitivity and constraints. We are also pursuing nanobridge junctions as a promising alternative to tunnel junctions, eliminating dielectric barriers and potentially reducing TLS -related loss. Beyond device-level improvements, our fabrication process is designed with scalability and foundry compatibility in mind, supporting reproducible and manufacturable superconducting quantum technologies. Finally, I will highlight our work on integrating control and readout electronics into the cryogenic environment, a key step toward compact, scalable quantum processors. Together, these developments support the global effort to push superconducting qubit platforms beyond current architectural and material limitations, paving the way toward more robust, scalable, and commercially viable quantum computing systems. Target applications include quantum simulation, combinatorial optimization, materials discovery, and fault-tolerant computing.