Title: Long-distance continuous-variable quantum key distribution using separable Gaussian states Show Chinese title

Title: 使用可分离高斯态的远距离连续变量量子密钥分发

Abstract: Continuous-variable quantum key distribution (CVQKD) is considered to be an alternative to classical cryptography for secure communication. However, its transmission distance is restricted to metropolitan areas, given that it is affected by the channel excess noise and losses. In this paper, we present a scheme for implementing long-distance CVQKD using separable Gaussian states. This tunable QKD protocol requires separable Gaussian states, which are squeezed and displaced, along with the assistance of classical communication and available linear optics compoments. This protocol originates from the entanglement of one mode and the auxiliary mode used for distribution, which is first destroyed by local correlated noises and restored subsequently by the interference of the auxillary mode with the second distant separable correlated mode. The displacement matrix is organized by two six-dimensional vectors and is finally fixed by the separability of the tripartite system. The separability between the ancilla and Alice and Bob's system mitigates the enemy's eavesdropping, leading to tolerating higher excess noise and achieving longer transmission distance. Show Chinese abstract

Abstract: 连续变量量子密钥分发（CVQKD）被认为是用于安全通信的经典密码学的替代方案。 然而，由于受到信道过量噪声和损耗的影响，其传输距离仅限于城区范围。 在本文中，我们提出了一种使用可分离高斯态实现远距离CVQKD的方案。 这种可调的QKD协议需要可分离的高斯态，这些态被压缩和位移，并借助经典通信和可用的线性光学组件的帮助。 该协议起源于用于分发的一个模式和辅助模式的纠缠，该纠缠首先被局部相关噪声破坏，随后通过辅助模式与第二个远距离可分离相关模式的干涉恢复。 位移矩阵由两个六维向量组成，并最终由三重系统的可分离性确定。 辅助系统与爱丽丝和鲍勃系统的可分离性减轻了敌方的窃听，从而容忍更高的过量噪声并实现更长的传输距离。