发表机构
Indian Institute of Technology Delhi; Centre for Applied Research in Electronics (CARE); Bharti School of Telecommunication Technology and Management; University of Melbourne（印度德里理工学院; 电子应用研究中心; Bharti电信技术与管理学院; 墨尔本大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文分析基于GHZ态的N方量子会议密钥协商在光纤信道中的有限密钥性能，提出含暗计数的信道模型并优化参数估计概率，数值显示距离和网络规模增大降低密钥率，优化可提升SKR并延长安全距离。
AI 中文摘要
量子会议密钥协商（QCKA）利用多方量子关联，使多个空间分离的用户能够以可组合的信息论安全性建立共同密钥。Greenberger--Horne--Zeilinger（GHZ）态是此任务的天然资源，但其在光纤上的分布会因传输损耗、偏振退相干和探测器缺陷而退化。我们研究了基于$N$-BB84协议的$N$方GHZ态QCKA系统的有限密钥性能，其中每条光链路通过扩展双粒子擦除-泡利信道以纳入探测器暗计数来建模。我们刻画了该量子信道对共享GHZ态的影响，并推导了错误率的闭式表达式。解析结果表明，本地比特错误率仅依赖于透射率和暗计数，而全局相位错误率在所有$N-1$条链路上复合，因此随距离和参与方数量的增加而更快退化。这些错误率被整合到有限密钥秘密密钥率（SKR）框架中，其中我们通过Brent无导数方法优化参数估计概率。数值结果表明，增加光纤距离和网络规模会降低可实现的SKR。此外，与固定分配基线相比，优化的参数估计概率持续提高SKR并延长最大安全距离，与渐近极限的比较量化了残余有限密钥惩罚。
英文摘要
Quantum conference key agreement (QCKA) enables multiple spatially separated users to establish a common key with composable information-theoretic security by exploiting multipartite quantum correlations. Greenberger--Horne--Zeilinger (GHZ) states are a natural resource for this task, but their distribution over optical fiber is degraded by transmission loss, polarization decoherence, and detector imperfections. We investigate the finite-key performance of an $N$-party GHZ-based QCKA system using the $N$-BB84 protocol, where each optical link is modeled by extending the bipartite erasure--Pauli channel to incorporate detector dark counts. We characterize the impact of this quantum channel on the shared GHZ state and derive closed-form expressions for the error rates. The analytical results reveal that the local bit-error rate depends only on transmissivity and dark counts, while the global phase-error rate compounds over all $N-1$ links and therefore degrades faster with both distance and the number of parties. These error rates are integrated into a finite-key secret-key-rate (SKR) framework, in which we optimize the parameter-estimation probability via Brent's derivative-free method. Numerical results show that increasing fiber distance and network size reduce the achievable SKR. Furthermore, the optimized parameter-estimation probability consistently increases the SKR and extends the maximum secure distance relative to a fixed-allocation baseline, with comparison to the asymptotic limit quantifying the residual finite-key penalty.
CommentsSubmitted to IEEE Transactions on Communications [Under Review]
