采用光子数编码的测量设备无关量子密钥分发协议突破无中继器界限
Surpassing the repeaterless bound with a photon-number encoded measurement-device-independent quantum key distribution protocol
AI总结：
本研究提出一种采用光子数编码的测量设备无关量子密钥分发协议，利用高维态与相干总光子数探测实现纠缠交换，可在现有技术下实现，能在更短距离突破纯损耗信道无中继器界限，总体传输距离优于现有同类协议。
摘要：
退相干对长距离量子密钥分发（QKD）具有不利影响。已提出的解决方案之一是使用量子中继器，其将用户间的总距离划分为多个更短的分段，以最小化信道损耗的影响。然而，中继器协议可实现的密钥率从根本上受限于每个相邻节点间的间距。本文提出一种测量设备无关协议，该协议采用由两个远距离可信方制备的高维态，并在中继站使用相干总光子数探测进行纠缠交换测量。我们提出了一种实验上可行的协议，由于所需的态在长距离下会衰减至单光子水平，因此可利用现有技术实现。该协议性能优于现有的测量设备无关QKD协议和双场QKD协议：它能在更短的距离下突破纯损耗信道的无中继器界限这一基本极限，并且在考虑实验 imperfections 时，总体可实现更长的传输距离。
英文摘要：
Decoherence is detrimental to quantum key distribution (QKD) over large distances. One of the proposed solutions is to use quantum repeaters, which divide the total distance between the users into smaller segments to minimise the effects of the losses in the channel. However, the secret key rates that repeater protocols can achieve are fundamentally bounded by the separation between each neighbouring node. Here we introduce a measurement-device-independent protocol which uses high-dimensional states prepared by two distant trusted parties and a coherent total photon number detection for the entanglement swapping measurement at the repeater station. We present an experimentally feasible protocol that can be implemented with current technology as the required states reduce down to the single-photon level over large distances. This protocol outperforms the existing measurement-device-independent and twin-field QKD protocols by surpassing the fundamental limit of the repeaterless bound for the pure-loss channel at a shorter distance and achieves a higher transmission distance in total when experimental imperfections are considered.
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