An iterative Ising decoder for quantum error correction codes
一种用于量子纠错码的迭代Ising解码器
Yuanqi Liu, Weilei Zeng, Peixiang Li, Yantong Liu, Guangyao Huang, Yingwen Liu, Dongyang Wang, Junjie Wu, Lingling Lao
AI总结 提出迭代低阶解码(ILOD)算法,通过交替求解X和Z子哈密顿量并利用贝叶斯先验近似交叉关联,将相互作用项的最大体数减半,加速求解器并降低自旋开销,在容错阈值和收敛性上接近或优于联合公式。
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- 12 pages, 8 figures, comments are welcome
Ising框架将量子纠错中的解码问题映射为经典哈密顿量的基态优化,其中$X$-$Z$误差关联作为交叉项出现。在现象学退极化噪声下,精确的联合公式对环面码包含高达8体相互作用,对$6.6.6$色码包含10体相互作用。这些高阶项会降低求解器收敛性,增加运行时间,并在嵌入到原生2体Ising硬件时提高辅助自旋开销。在这项工作中,我们提出了迭代低阶解码(ILOD)算法,它在$X$型和$Z$型子哈密顿量之间交替,通过贝叶斯先验近似交叉型关联,该先验利用另一种类型的推断误差配置重新加权每种类型的耦合。这将哈密顿量中相互作用项的最大体数减半,加速了求解器,在更大码距下恢复收敛性,并将2体嵌入的总自旋数减少了2.5倍。对于环面码,ILOD达到4.73%的阈值,而联合公式为4.83%,经验运行时间比按$(0.81)^d$缩放。对于$6.6.6$色码,在小码距下它们的阈值在统计不确定性内一致,并且ILOD在更大码距下保持收敛,而联合公式尽管有更大的退火预算却无法收敛。
The Ising framework maps the decoding problem in quantum error correction onto ground-state optimization of a classical Hamiltonian, in which $X$-$Z$ error correlations enter as cross terms. Under phenomenological depolarizing noise, the exact joint formulation contains up to 8-body interactions for the toric code and 10-body for the $6.6.6$ color code. These high-order terms degrade solver convergence, inflate runtime, and raise the auxiliary spin overhead when embedding into native 2-body Ising hardware. In this work, we propose the iterative low-order decoding (ILOD) algorithm, which alternates between $X$- and $Z$-type sub-Hamiltonians, approximating cross-type correlations through Bayesian priors that reweight each type's couplings using the other type's inferred error configuration. This halves the maximum body count of interaction terms in the Hamiltonian, accelerating the solver, restoring convergence at larger code distances, and reducing the total spin count for 2-body embedding by a factor of $2.5$. For the toric code, ILOD attains a threshold of $4.73%$ versus $4.83%$ for the joint formulation, with the empirical runtime ratio scaling as $(0.81)^d$. For the $6.6.6$ color code, their thresholds agree within statistical uncertainty for small code distances, and ILOD remains convergent for larger distances where the joint formulation fails to converge despite a larger annealing budget.