Quasiparticle Dynamics in Niobium and Tantalum-Based Superconducting Quantum Devices

Superconducting quantum circuits are a leading platform for both noisy intermediate-scale quantum (NISQ) computing and fault-tolerant error-corrected quantum computing. Yet quasiparticle tunneling across Josephson junctions remains a significant source of errors, disrupting both the energy and phase coherence of the circuits. In this study, we investigate quasiparticle generation and dynamics using niobium and tantalum-based devices with Al/AlOx/Al tunnel junctions serving as charge-parity detectors. Our findings reveal that tantalum-based qubits exhibit greater sensitivity to infrared radiation. By employing both thermal and monochromatic terahertz infrared (IR) sources, we explore the susceptibility of the devices to IR radiation. We report best practices for mitigating background radiation and present measurements of the infrared environment over periods of days and weeks. We further discuss the observed quasiparticle rates in relation to the superconducting material properties, such as quasiparticle lifetime and mobility, and highlight strategies for optimizing device design.