Efficient Quantum Key Distribution

研究问题正交调制光相干通信是一种针对传统100 G互联网流量的成熟通信方案。但是，在极低的信号强度下，光的固有量子特性（如真空噪声）占主导地位，并阻止有意义的信息交换。然而，有可能利用和利用这种量子不确定性，使其用于安全的密钥分发。连续变量量子密钥分发（CV-QKD）是一种高效的量子技术，可以在密集波分复用（DWDM）网络中实现量子信道和传统信道的共存，而收敛于相干通信的CV-QKD本地振荡器（LLO）方案近年来受到人们的关注。它们为测试和评估用于分发量子信号的相干通信技术的性能提供了极好的机会。然而，这些方法的最近的演示已被限制到低损耗信道与降低的密钥速率，由于升高的接收机noise.Approach/MethodologyThis项目的目的是开发新的CV-QKD LLO计划的高信道损耗的应用增强安全的密钥速率。从噪声相干接收机中恢复量子信号信息将是这一工作的一个方向。在这个项目中，学生将在非常低的接收器噪声下测量量子信道，以展示高性能操作的潜力。降低噪声和优化CV-QKD参数将是这一发展的主要考虑因素。这项研究将扩展到多发射机或多维量子信号检测，以提高安全密钥带宽。链路上的工作将首先集中在测量噪声，然后推断各种量子攻击下可能的安全密钥速率。然而，一旦这个初始阶段完成，学生将在一个链接上工作，该链接提取出一个真实的安全密钥，该密钥可用于对现有剑桥量子网络上的传统信道进行编码。在该项目的后期，将调查利用国家暗纤维设施扩大到全国规模的可行性。这项研究主要是实验性的，使用剑桥CV-QKD系统，但适度的理论研究也是必要的。它将连接到主要的EPSRC量子技术中心QComm 2。

Research questionCoherent communication with quadrature modulated light is a well-developed communication scheme for conventional 100G internet traffic. But, at extremely low signal strength, inherent quantum features of light such as vacuum noise dominate and prevent the exchange of meaningful messages. However, it is possible to harness and exploit this quantum uncertainty to make it useful for secure key distribution. Continuous Variable Quantum Key Distribution (CV-QKD) is such a quantum technology which is also highly efficient for deployment in DWDM networks such that quantum and conventional channels can co-exist.CV-QKD Local Local Oscillator (LLO) schemes that converge to coherent communication have recently been gaining interest. They open up an excellent opportunity for testing and evaluating the performance of coherent communication techniques for distributing quantum signals. However, recent demonstrations of these approaches have been limited to low loss channels with reduced key rates, due to elevated receiver noise.Approach/MethodologyThis project aims to develop new CV-QKD LLO schemes for high channel loss applications with enhanced secure key rates. One direction of this work will be to recover the quantum signal information from a noisy coherent receiver. Within this project, the student will work on measurement of the quantum channel at very low receiver noise to demonstrate the potential for high performance operation. Noise reduction and optimization of CV-QKD parameters will be the major consideration for this development. This study will be extended to multi transmitter or multidimensional quantum signal detection to enhance the secure key bandwidth.The work on the link will initially focus on measuring the noise and then extrapolating to the possible secure key rate under various quantum attacks. However, once this initial phase is complete the student will then work on a link that distils a real secure key that can be used to encode conventional channels on the existing Cambridge quantum network. Later in this project, the feasibility of extended to a national scale using the National Dark Fibre Facility will be investigated. This research is primarily experimental, using the Cambridge CV-QKD system, but moderate theoretical study is also necessary. It will be linked to the major EPSRC Quantum Technology Hub, QComm2.