Error-corrected quantum computers can only work if errors are small and uncorrelated. Here I show how cosmic rays or stray background radiation affects superconducting qubits by modeling the phonon to electron/quasiparticle down-conversion physics. For present designs, the model predicts about 57\% of the radiation energy breaks Cooper pairs into quasiparticles, which then vigorously suppress the qubit energy relaxation time (T1∼ 160 ns) over a large area (cm) and for a long time (ms). Such large and correlated decay kills error correction. Using this quantitative model, I show how this energy can be channeled away from the qubit so that this error mechanism can be reduced by many orders of magnitude. I also comment on how this affects other solid-state qubits.
@article{arxiv.2012.06137,
title = {Saving superconducting quantum processors from qubit decay and correlated errors generated by gamma and cosmic rays},
author = {John M. Martinis},
journal= {arXiv preprint arXiv:2012.06137},
year = {2021}
}