Expanded microphysical modeling of disruptive events in superconducting qubit devices

Recent advances in superconducting qubit design and fabrication processes, including gap engineering efforts and normal-metal phonon downconverters, have led to an increase in the robustness of superconducting qubits against ionizing radiation and other disruptive in-chip events. Further improvements rely on a combination of refined qubit design, fabrication, testing, and modeling to quantify the degree of harm that disruptive events cause in a given device. In this talk, we present major upgrades to the G4CMP Monte-Carlo toolkit used for modeling impacts in superconducting devices with arbitrary detector geometries. New processes modeled include Cooper-pair-breaking by phonons, the ensuing quasiparticle downconversion cascade, and quasiparticle tracking and spatial diffusion in thin films. We present these upgrades in the context of a few applications of relevance to the QIS field's attempts to design more robust superconducting devices.