In the practical continuous-variable quantum key distribution (CV-QKD) system, the postprocessing process, particularly the error correction part, significantly impacts the system performance. Multi-edge type low-density parity-check (MET-LDPC) codes are suitable for CV-QKD systems because of their Shannon-limit-approaching performance at a low signal-to-noise ratio (SNR). However, the process of designing a low-rate MET-LDPC code with good performance is extremely complicated. Thus, we introduce Raptor-like LDPC (RL-LDPC) codes into the CV-QKD system, exhibiting both the rate compatible property of the Raptor code and capacity-approaching performance of MET-LDPC codes. Moreover, this technique can significantly reduce the cost of constructing a new matrix. We design the RL-LDPC matrix with a code rate of 0.02 and easily and effectively adjust this rate from 0.016 to 0.034. Simulation results show that we can achieve more than 98% reconciliation efficiency in a range of code rate variation using only one RL-LDPC code that can support high-speed decoding with an SNR less than −16.45 dB. This code allows the system to maintain a high key extraction rate under various SNRs, paving the way for practical applications of CV-QKD systems with different transmission distances.

在实际的连续可变量子密钥分发（CV-QKD）系统中，后处理过程（尤其是纠错部分）会严重影响系统性能。多边缘型低密度奇偶校验（MET-LDPC）代码适用于CV-QKD系统，因为它们在低信噪比（SNR）时具有接近Shannon极限的性能。但是，设计具有良好性能的低速率MET-LDPC代码的过程非常复杂。因此，我们将类猛禽LDPC（RL-LDPC）代码引入CV-QKD系统，既展现了猛禽代码的速率兼容特性，又展现了MET-LDPC代码的逼近性能。而且，该技术可以显着降低构建新矩阵的成本。我们设计的RL-LDPC矩阵的编码率为0。02并轻松有效地将该比率从0.016调整为0.034。仿真结果表明，仅使用一个可以支持SNR低于−16.45 dB的高速解码的RL-LDPC码，我们就可以在一定的码率变化范围内实现98％以上的协调效率。该代码允许系统在各种SNR情况下保持较高的密钥提取率，从而为具有不同传输距离的CV-QKD系统的实际应用铺平了道路。