Impact of quasiparticle pumping on the recovery time of catastrophic bursts of globally suppressed relaxation time in few-qubit superconducting processors with different Josephson-junction types.

We resolve global bursts of suppressed qubit relaxation time in 5- and 7-transmon devices, focusing on a few factors that affect the recovery time to equilibrium. These factors are the rate of applied qubit flips in the detection scheme, and the type of Josephson junctions employed (Dolan-bridge or Manhattan). In the 5-qubit device, with Dolan junctions, we observe that the recovery time can be accelerated from ~1.5 ms to ~400 µs by increasing the rate of applied flips. In contrast, in the 7-qubit chip, the recovery time is robustly ~250 µs, independent of flip rate. We attribute these observations to differences in quasiparticle pumping mechanisms for the two junction types.