Speaker
Description
Ionizing radiation incident on a superconducting qubit chip can cause phonon excitations and trapped charges. The phonon can generate non-equilibrium quasiparticles in the superconductor near the qubit island, which can tunnel across the junction, interacting with the qubit energy and changing the parity of the qubit. Trapped charges change the electric field environment in nearby qubits and are seen as charge noise in charge-sensitive qubits. High-energy interactions can cause these behaviors to manifest across multiple qubits on the same chip, correlated to space and time. Previously, we have seen an excess of charge noise events in low-background measurements, not explained by ionizing gammas. We are continuing to study these behaviors using multiple detection channels on two devices with different sensitivities in our low-background underground environment. Using an array of weakly charge-sensitive aluminum qubits, we are examining the long-term effect of ionizing radiation on the stability of qubit gate charge. We are also measuring charge jump and parity switching rates on an array of aluminum SQUATs to understand their sensitivity to gamma radiation.
