Understanding quasiparticle dynamics in a superconducting qubit through phonon burst-induced correlated errors

When an ionizing particle interacts with the substrate of a superconducting qubit chip, it generates high-energy athermal phonons that propagate through the material, breaking Cooper pairs in the superconducting films and inducing quasiparticle poisoning. These non-equilibrium quasiparticles limit qubit coherence times and introduce correlated errors across large qubit arrays, posing a major challenge for the development of fault-tolerant quantum computers. At the same time, the potential sensitivity of superconducting qubits to Cooper pair breaking makes them promising detectors for dark matter and coherent elastic neutrino–nucleus scattering, given the meV-scale energy required for quasiparticle generation in most superconductors. In this work, we present a detailed statistical analysis of radiation-induced relaxation errors aimed at modeling the time evolution of quasiparticle density dynamics. From experimental data on five ground-plane transmon qubits, we extract the quasiparticle recombination constant with a precision of ≤10%. Furthermore, we investigate the correlation between the linear loss rate and the energy deposited in the qubit island. Finally, we introduce a statistical reconstruction method based on position localization to estimate the total energy deposited on the chip, providing a pathway toward using superconducting qubits as sensitive particle detectors.