Handling leakage with subsystem codes

Journal Article (Journal Article)

Leakage is a particularly damaging error that occurs when a qubit state falls out of its two-level computational subspace. Compared to independent depolarizing noise, leaked qubits may produce many more configurations of harmful correlated errors during error-correction. In this work, we investigate different local codes in the low-error regime of a leakage gate error model. When restricting to bare-Ancilla extraction, we observe that subsystem codes are good candidates for handling leakage, as their locality can limit damaging correlated errors. As a case study, we compare subspace surface codes to the subsystem surface codes introduced by Bravyi et al. In contrast to depolarizing noise, subsystem surface codes outperform same-distance subspace surface codes below error rates as high as 7.5 × 10-4 while offering better per-qubit distance protection. Furthermore, we show that at low to intermediate distances, Bacon-Shor codes offer better per-qubit error protection against leakage in an ion-Trap motivated error model below error rates as high as 1.2 × 10-3. For restricted leakage models, this advantage can be extended to higher distances by relaxing to unverified two-qubit cat state extraction in the surface code. These results highlight an intrinsic benefit of subsystem code locality to error-corrective performance.

Full Text

Duke Authors

Cited Authors

  • Brown, NC; Newman, M; Brown, KR

Published Date

  • July 30, 2019

Published In

Volume / Issue

  • 21 / 7

International Standard Serial Number (ISSN)

  • 1367-2630

Digital Object Identifier (DOI)

  • 10.1088/1367-2630/ab3372

Citation Source

  • Scopus