PreprintCC BY 4.0arXiv
Correlated decoding loses the surface code's effective distance below threshold
Abstract
Correlated decoding improves matching and clustering surface-code decoders by reweighting one decoding subgraph conditioned on the other's correction. We show that standard reweighting can cause correlated decoders to fail on size-(d−1)/2 fault configurations that a distance-d code should correct, reducing error suppression deep below threshold. Under circuit-level noise, a single first-pass edge can discount several correlated edges, even though their joint occurrence requires additional independent faults, so the decoder favors an over-discounted correction. Regularizing the reweighting rule restores the nominal distance scaling and a clear correlated-decoding advantage.
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BibTeX
@misc{fuente2026correlated,
title = {{Correlated decoding loses the surface code's effective distance below threshold}},
author = {César Hernando de la Fuente and Joonas Majaniemi and Evert van Nieuwenburg and Felix Frohnert},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.26785},
eprint = {2610.26785},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.26785},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Correlated decoding loses the surface code's effective distance below threshold
AU - César Hernando de la Fuente
AU - Joonas Majaniemi
AU - Evert van Nieuwenburg
AU - Felix Frohnert
PY - 2026
DA - 2026/10/19
PB - arXiv
DO - 10.48550/arxiv.2610.26785
UR - https://arxiv.org/abs/2610.26785
AB - Correlated decoding improves matching and clustering surface-code decoders by reweighting one decoding subgraph conditioned on the other's correction. We show that standard reweighting can cause correlated decoders to fail on size-(d−1)/2 fault configurations that a distance-d code should correct, reducing error suppression deep below threshold. Under circuit-level noise, a single first-pass edge can discount several correlated edges, even though their joint occurrence requires additional independent faults, so the decoder favors an over-discounted correction. Regularizing the reweighting rule restores the nominal distance scaling and a clear correlated-decoding advantage.
ER -