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1、中国科学技术大学 博士学位论文 光纤量子密钥分配关键技术研究 姓名：王双 申请学位级别：博士 专业：光学 指导教师：韩正甫;郭光灿 2011-04 摘 要 - I - 摘摘 要要 几千年来，密码学一直在国防、军事、外交等领域发挥着重要作用。随着 计算机和互联网技术的发展，密码学在我们的日常生活中也起到不可或缺的作 用。密码学的基本目的就是使得通信双方能够通过不安全的信道安全地传送信 息，这就有赖于通信双方使用的密码体制，现有的密码体制主要有两大类 “对称密钥密码体制”和“公钥密码体制” 。量子计算机的提出和量子算法的出 现，给这两种密码体制都带来了巨大的潜在安全威胁。 “一次一密”密码体制是密
2、码学中惟一被证明安全的密码体制，但其却存 在密钥分配的难题。量子密钥分配的出现无疑解决了这一难题。量子密钥分配 以量子理论为基础，可以在不安全的公共信道上安全地实时分配密钥。因此， 将量子密钥分配与一次一密相结合， 就可以完美地实现无条件安全的保密通信。 量子密钥分配自 1984 年提出以来，一直受到广泛关注，世界各国均投入大 量人力物力进行研究，经过二十几年的发展，无论在理论还是在实验方面均取 得了巨大的进展。目前，量子密钥分配正向实用化方向发展。本文以光纤量子 密钥分配关键技术为主要研究内容，包括端到端量子密钥分配系统的高速远距 离实现技术和量子密钥分配网络的组网技术， 主要研究成果分为以
3、下六个方面： 1、 在标记单光子源诱骗态实验的基础上，分析光强波动这一实际问题，对比 弱相干态光源和标记单光子源， 发现标记单光子源是一种好的诱骗态实验光 源，它不仅有更长的安全传输距离，而且受光强波动的影响比弱相干态光源 更小。 2、 在已有 Faraday-Michelson 干涉环量子密钥分配系统的基础上，改进系统结 构，提出参数选择判据，将系统速率提高到 20MHz，并将其应用到实地量 子密钥分配网络中。 3、 基于不等臂 Faraday-Michelson 干涉环结构，在实验室内用波形发生器、超 导单光子探测器和时间数字转换器等仪器搭建出一套高速差分相位量子密 钥分配系统，系统速率达
4、到 2GHz，标准单模光纤传输距离长达 260 公里， 信道衰减达 52.9dB， 将国际量子密钥分配实验最大信道衰减提高一个数量级。 4、 提出用连续光进行量子密钥分配的方案。此方案在高速远距离量子密钥分 配中有很大的优势，使用连续光后，发射端控制系统会变得简单，信号的光 摘 要 - II - 谱质量会更好，信道的色散展宽效应会大大减弱。然后，通过用连续光实现 差分相位量子密钥分配对该方案进行了可行性检验。 5、 在芜湖电信光网络上设计和搭建出多层级量子政务网。该量子密钥分配网 络有七个用户节点，其中五个在芜湖市的政府部门内。根据优先级，将全网 用户分成两个层级骨干量子密钥分配网络和量子密钥
5、分配子网， 其中骨 干量子密钥分配网络是以量子路由器为核心构建的全时全通网络， 量子密钥 分配子网是以程控量子交换机为核心构建的时分复用网络， 两个层级的量子 密钥分配网络以可信任中继的方式融合在一起。 6、 提出波长节约型全时全通量子路由器方案，与之前我们小组提出的全时全 通量子路由器相比，能节约 50%75%的波长资源。通过分析拓扑结构，发 现波长节约型全时全通量子路由器对应的图论模型， 并提出两种简单易行的 量子路由器内部连接方式。同时，在芜湖电信光网络上利用新的全时全通路 由器搭建出波长节约型全时全通量子密钥分配网络， 该网络由五个节点组成， 仅需两个波长进行路由， 线路链接的量子密钥
6、分配系统速率 20MHz。 此外， 还通过简化量子密钥分配网络，提出插入损耗和串扰的分析模型，对量子密 钥分配网络进行性能分析。 关键词：关键词：量子密钥分配，量子密码，量子密钥分配网络，量子路由器 Abstract - III - ABSTRACT For thousands of years, cryptography always plays an important and unique role in defense, military, and diplomatic fields. With the development of computer and internet tech
7、nology, cryptography also plays an indispensable role in our daily life. The basic purpose of cryptography is securely transmitting confidential information over an insecure channel, which depends on the apllied cryptosystem. There are two main cryptosystems, one is symmetric key cryptosystem, the o
8、ther one is public cryptosystem. The idea of quantum computer and quantum algorithms bring tremendous potential threaten to these two cyptosytems. The only proved secure cryptosystem is one-time pad, but it has the problem of key distribution. Quantum key distribution (QKD) can perfectly solve this
9、problem. Base on the quantum theory, QKD can make enables two participants to share secure keys over an insecure public channel in real time. Therefore, combing QKD with the one-time pad cryptosystem, we can perfectly achieve unconditional secure communication. Since 1984, QKD has attracted a widesp
10、read concern, and many countries have put a lot of effort into the QKD research field. After the past two decades of developments, QKD has achieved significant improvements, both in theory and in experiments. The current QKD research is towards practicability. During my Ph.D period, key technologies
11、 of optical fiber QKD are the main research contents, including high-speed QKD system over long distance and networking technology of QKD network. The major results are outlined as follows: 1. Based on the previous decoy state QKD experiment with the heralded single-photon source, we recalculated th
12、e secure rates in the case of intensity fluctuations. Compared with the weak coherent source, we found that the heralded single-photon source was a good source for decoy state QKD, since it not only has larger upper bound of transmission distance, but also more robust against intensity fluctuations.
13、 2. We improved the Faraday-Michelson QKD system, including the optical fiber system and the electronic control system. The speed of the improved QKD system increased to 20 MHz, and we applied the improved QKD system in the wavelength-saving QKD network. 3. Based on the Faraday-Michelson interferome
14、ter, a differential phase shift (DPS) QKD system with the pattern generator, the superconducting single photon detector Abstract - IV - and the time-to-digit convertor was implemented. The clock rate of the system is 2 GHz, and the key was distributed over 260 km standard single mode fiber with 52.9
15、 dB channel loss, of which the loss is one order of magnitude larger than previous record. 4. A QKD protocol with continuous wave was proposed. QKD with continuous wave is not only a new idea, but also has practical values for high-speed, long-distance systems. With continuous wave, the QKD system b
16、ecomes very simple, and has better signal quality in optical spectrum domain, and can greatly reduce the chromatic dispersion of optical fiber. Then, the feasibility was tested by implementing the DPS QKD with continuous wave. 5. A robust hierarchical metropolitan QKD network was designed and built on the commercial fiber network of China Telecom Corporation Limited, in Wuhu. There are seven nodes in the QKD network, and five of them are in the government department. According to the pri
