Koki Okada, Kenta Kasai (Apr 23 2026).
Abstract: We construct a quantum low-density parity-check code family from a length-512 Calderbank-Shor-Steane base matrix pair. The base pair is
(3,8)-regular, both Tanner graphs have girth 8 , and the base code has parameters
[[512,174,8]]. The construction uses affine cosets of six 3-dimensional subspaces of
F29 as check supports, and then applies circulant permutation matrix (CPM) lifts. The main decoding experiment uses the CPM-lifted code with lift factor
P=32, which has parameters
[[16384,4142,≤40]], under the code-capacity depolarizing model. A belief-propagation decoder with post-processing achieved frame error rate about
10−8 at
p= 0.085 , and one observed logical residual of weight 40 gives a decoder-derived upper bound
d≤40.
