量子编码定理证明信道在没有辅助资源的情况下其量子容量等于规整化相干信息的最大值。一般泡利信道是最普遍使用的信道模型,其量子容量目前无法准确计算,只能用多信道相干信息去逼近。本文应用量子图态级联编码,得到一般泡利信道在该编码输入下的多信道相干信息的公式,能够有效计算一般泡利信道量子容量的逼近值和信道传输量子信息的噪声容限。计算速度比Monte Carlo算法提高三个数量级。

Quantum capacity of a channel is the maximal quantum information that can be reliably transmitted. Quantum coding theorem shows that quantum capacity of a channel without additional resources is equal to the regularized coherent information. The generic Pauli channel is the most popular model in practice,and its quantum capacity cannot be evaluated exactly,but rather can only be approached by using multichannel coherent information. In this paper,we used concatenate graph state code to obtain formulae of coherent information for generic Pauli channels,by which we could find the approach value of quantum capacity and the noise tolerance of the channel efficiently.