Robust NbN‐on‐Si/SiGe Hybrid Microwave Quantum Circuits With Long‐Term Stability

ABSTRACT Large‐scale quantum computing requires superconducting microwave circuits that simultaneously exhibit ultra‐low loss, long‐term reliability, and scalable integration with semiconductor technologies. Achieving these capabilities within a CMOS‐compatible platform remains a major challenge, with microwave losses arising from material defects, interfaces, and fabrication processes limiting scalability. Here, we demonstrate robust niobium nitride (NbN) coplanar waveguide resonators fabricated on Si/SiGe quantum‐well heterostructures, establishing a hybrid superconducting–semiconducting microwave platform compatible with scalable silicon quantum technologies. Using temperature‐dependent microwave spectroscopy from the millikelvin regime to kelvin in the single‐photon limit, we systematically identify the dominant dissipation mechanisms governing device performance, including two‐level systems, quasiparticles, and interface‐related scattering, and correlate their contributions with wafer properties and fabrication routes. Despite the complexity of the hybrid architecture, the devices exhibit reproducible low‐loss microwave characteristics and maintain stable operation for more than two years without measurable degradation, demonstrating exceptional robustness under realistic operating conditions. Our analysis provides quantitative design principles for minimizing microwave loss in hybrid superconducting–semiconducting circuits while preserving compatibility with semiconductor quantum hardware. These results demonstrate the potential of NbN‐on‐Si/SiGe technology as a reliable and scalable microwave platform for monolithically integrated quantum processors, providing a practical route toward large‐scale fault‐tolerant quantum computing.