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arXiv · 2509.01892

Accelerating BP-based decoders for QLDPC Codes with Local Syndrome-Based Preprocessing

Wenxuan Fan·Yasunari Suzuki·Gokul Subramanian Ravi·Yosuke Ueno·Ilkwon Byun·Koji Inoue·Teruo Tanimoto
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Abstract

Due to the high error rate of qubits, detecting and correcting errors is essential for achieving fault-tolerant quantum computing (FTQC). Quantum low-density parity-check (QLDPC) codes are one of the most promising quantum error correction (QEC) methods due to their high encoding rates. BP (Belief Propagation)-based decoders are widely used and highly competitive for QLDPC codes because BP offers inherent parallelism and strong scalability. However, BP-based decoders still suffer from high decoding latency, a large portion of which is spent in the iterative BP stage. In this paper, we propose a lightweight preprocessing step that utilizes local patterns in the syndrome to detect likely trivial error events and provide them as hints to BP-based decoders. These hints accelerate BP convergence and thereby reduce the overall decoding time. The proposed preprocessing step offers a broadly compatible approach to reducing the latency of BP-based QLDPC decodes. On the bivariate bicycle code $[[144,12,12]]$ at low physical error rates, our method achieves a $10\times$ speedup in decoding time for BP-OSD, and more than $2\times$ speedup for both BP-LSD and Relay-BP. Our method maintains the logical error rate when combined with BP-OSD and Relay-BP, while further achieving a significant reduction in logical error rate when combined with BP-LSD.

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Wenxuan Fan, Yasunari Suzuki, Gokul Subramanian Ravi, Yosuke Ueno, Ilkwon Byun, Koji Inoue, Teruo Tanimoto. 2025-09-02. Accelerating BP-based decoders for QLDPC Codes with Local Syndrome-Based Preprocessing. https://arxiv.org/abs/2509.01892

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