Robust NbN on Si-SiGe hybrid superconducting-semiconducting microwave quantum circuit

Abstract

Advancing large-scale quantum computing requires superconducting circuits that combine long coherence times with compatibility with semiconductor technology. We investigate niobium nitride (NbN) coplanar waveguide resonators integrated with Si/SiGe quantum wells, creating a hybrid platform designed for CMOS-compatible quantum hardware. Using temperature-dependent microwave spectroscopy in the single-photon regime, we examine resonance frequency and quality factor variations to probe the underlying loss mechanisms. Our analysis identifies the roles of two-level systems, quasiparticles, and scattering processes, and connects these losses to wafer properties and fabrication methods. The devices demonstrate reproducible performance and stable operation maintained for over two years, highlighting their robustness. These results provide design guidelines for developing low-loss, CMOS-compatible superconducting circuits and support progress toward resilient, scalable architectures for quantum information processing.