Speaker
Description
Quantum error correction fundamentally requires that physical errors are sufficiently uncorrelated in time and space. In superconducting qubit processors, impacts from ionizing radiation violate this assumption by elevating quasiparticle density across the substrate, triggering correlated qubit error bursts. Previously, we demonstrated that the most damaging of these—correlated T1 errors originating from quasiparticle tunneling—can be strongly suppressed by engineering the superconducting gap profile at the Josephson junctions. Here, we present our group's recent findings on a new mechanism of impact-induced correlated errors that persists despite gap engineering. We observe that radiation impacts systematically shift the frequencies of affected qubits by up to 3 MHz for ~1 ms, resulting in correlated phase errors. We provide evidence that these shifts stem from quasiparticle-qubit interactions in the junction region, and we demonstrate that these shift-induced phase errors can be detrimental to the performance of QEC protocols.