Restart Belief: A General Quantum LDPC Decoder

Hardware-friendly quantum low-density parity-check (QLDPC) decoders are commonly built upon belief propagation (BP) processing. Yet, quantum degeneracy often prevents BP from achieving reliable convergence. To overcome this fundamental limitation, we propose the restart belief (RB) decoder, an iterative BP-based algorithm inspired by branch-and-bound optimization principles. We show that, for the considered QLDPC codes, the RB decoder achieves fast convergence and significantly improved decoding accuracy compared to existing decoders in the literature, while guaranteeing the error correction capability.