在连续变量量子密钥分发(CVQKD)多维数据协调过程中,低密度奇偶校验码(LDPC)的纠错性能直接影响协调效率和传输距离。构造了一种双边类型的低密度奇偶校验码(TET-LDPC),引入了类似于重复累积码中的累积结构以提高其纠错性能,在多维数据协调算法中得到了更小的收敛信噪比、更高的协调效率以及更远的传输距离。仿真结果表明:当TET-LDPC的码率为0.5,分组码长为2×10 ⁵时,收敛信噪比降至1.02 dB,协调效率达到了98.58%,安全密钥率达到17.61 kb/s, CVQKD系统的传输距离提高为44.9 km。

In the multidimensional reconciliation process of continuous-variable quantum key distribution (CVQKD), the error correction performance of the low-density parity-check code (LDPC) directly affects the reconciliation efficiency and transmission distance. Herein, a two-edge type low-density parity-check code (TET-LDPC) is constructed. We introduce a cumulative structure similar to that of a repeat-accumulate code into the TET-LDPC to improve its error correction performance. These codes obtain a smaller convergence signal-to-noise ratio, whereas the reconciliation system achieves higher coordination efficiency and longer transmission distance. The simulation results indicate that at a TET-LDPC code rate of 0.5 and a block length of 2×10 5, the convergence signal-to-noise ratio of the system is reduced to 1.02 dB, the data reconciliation efficiency is 98.58%, the security key rate reaches 17.61 kb/s, and the CVQKD transmission distance increases to 44.9 km.