Jason Chadwick
Jason D. Chadwick
Quantum computing Ph.D. student
University of Chicago

Google Scholar

Fault-tolerant quantum computation relies on the assumption of time-invariant, sufficiently low physical error rates. However, current superconducting quantum computers suffer from frequent disruptive noise events, including cosmic ray impacts and shifting two-level system defects. Several methods have been proposed to mitigate these issues in software, but they add large overheads in terms of physical qubit count, as it is difficult to preserve logical information through such a large error event.

We focus on mitigating multi-qubit burst errors in magic state factories, which are expected to comprise up to 95% of the spacetime cost of future quantum programs. Our key insight is that magic state factories do not need to preserve logical information over time; once we detect an increase in local physical error rates, we can simply turn off parts of the factory that are affected, re-map the factory to the new chip geometry, and continue operating. This is much more efficient than previous general methods that attempt to preserve the information encoded within logical qubits, and is resilient even under many simultaneous impact events. Using precise physical noise models, we show an efficient ray detection method and evaluate our strategy in different noise regimes. Compared to the best existing baselines, we find reductions in ray-induced overheads by several orders of magnitude, yielding reductions in total qubitcycle cost by geomean 6.5x to 13.8x depending on the noise model. This work reduces the burden on hardware by providing low-overhead software mitigation of these errors.