Correlated quasiparticle poisoning from phonon-only events in superconducting qubits

abstract: Throughout multiple cooldowns we observe a power-law reduction in time for the rate of multiqubit correlated poisoning events, while the rate of shifts in qubit offset-charge remains constant; evidence of a non-ionizing source of pair-breaking phonon bursts for superconducting qubits. We investigate different types of sample packaging, some of which are sensitive to mechanical impacts from the cryocooler pulse tube. One possible source of these events comes from relaxation of thermallyinduced stresses from differential thermal contraction between the device layer and substrate.