Probing non-equilibrium quasiparticle dynamics in transmon qubits: Part 1*

Non-equilibrium quasiparticle excitations negatively affect the performance of superconducting devices. Although the source of non-equilibrium quasiparticles is not well understood, the severity of their effect can be mitigated by improved filtering and device design. We implement Ti-proximitized Al quasiparticle traps aimed at reducing the density of quasiparticles in sensitive regions of superconducting devices. To characterize these traps, we detect individual quasiparticle tunneling events in an offset-charge-sensitive 3D transmon qubit, and correlate these events with qubit transitions. These measurements probe the limit on transmon coherence imposed by quasiparticles, and offer insight into the quasiparticle energy distribution. This talk will focus on experimental design and measurement methods.