Hybrid Quantum-Classical Communication Networks

信息安全是当今复杂社会的必然要求。无论是我们的个人信息、银行交易，还是一些机密的军事通信，它们都依赖于密码技术，以保证发送者和目标接收者之间的安全通信。然而，这种保证不一定会永远持续下去。技术的进步已经使许多旧的密码系统过时，预计未来的发现也将使当前的安全通信方法变得不可靠。特别是，基于量子力学定律的新计算范例的发展对广泛使用的公钥密码系统的安全性构成了威胁。幸运的是，量子力学可以用一只手拿到什么，它用另一只手回馈。利用量子密钥分发(QKD)协议实现的保密通信是量子信息发展领域最紧迫的应用。QKD提供牢不可破的、面向未来的、安全的安全，不受目前运行中的大多数密码系统的漏洞的影响。在这一点上，QKD已经在专用通道上和双方之间实现。在利用目前的通信漏洞之前，必须通过网络为任意距离的任何两个公共用户使用QKD技术提供便利。这个悬而未决的问题存在于量子物理和光通信工程的交叉点上，因为所有已知的QKD协议都依赖于光传输。这项建议侧重于当多个用户希望将相同的基础设施(即光纤)用于经典和量子通信应用时出现的问题。这在本质上类似于经典的多址问题，例如移动通信，其中多个用户通过共享通信信道进行通信。在混合量子-经典网络中，这一特征必须扩展到包括量子密钥分发应用，在这些应用中，我们处理像单个光子一样弱的光信号。在这个项目中，我的目标是对混合量子-经典网络的一系列网络配置和不同的多址技术进行理论研究。该项目将阐明支撑未来实施的必要步骤。我还将讨论目前仅支持经典应用的光通信网络与未来将同时提供数据传输服务和QKD驱动的安全通信的混合网络的兼容性问题。这将使国家范围内的远程经典量子通信成为可能。

Information security is a necessity of today's complex society. Let it be our personal information, a bank transaction, or some confidential military correspondence, they all rely on cryptographic techniques that guarantee secure communication between the transmitter and the intended receiver. This assurance, however, does not necessarily last forever. Technological advancements have already made many older cryptosystems obsolete, and it is anticipated that future discoveries will make the current secure communication methods unreliable as well. In particular, the development of new computational paradigms based on the laws of quantum mechanics is a threat to the security of the widely used public-key cryptosystems. Fortunately, what quantum mechanics may take by one hand, it gives back with the other. Secure communication, facilitated by the use of quantum key distribution (QKD) protocols, is the most imminent application of the developing field of quantum information. QKD provides unbreakable, future-proof, security safe from the vulnerabilities of most cryptosystems currently in operation. To this point, QKD has been implemented over dedicated channels and between two parties. Before current communication vulnerabilities are exploited, it is essential to facilitate the use of QKD technology for any two public users at any distance, via a network. This unsolved problem lies at the intersection of quantum physics and optical communications engineering, as all known QKD protocols rely on light transmission. This proposal focuses on the problems that arise when multiple users wish to utilise the same infrastructure, namely, optical fibre, for both classical and quantum communication applications. This is in essence similar to a classical multiple-access problem, such as mobile communication, where multiple users communicate via a shared communication channel. In hybrid quantum-classical networks, this feature must be extended to include QKD applications, where we are dealing with optical signals as weak as a single photon.In this project, I aim at undertaking a theoretical study of a range of network configurations and different multiple-access techniques for hybrid quantum-classical networks. This project will shed light on the necessary steps that underpin future implementations. I will also look at compatibility issues regarding the integration of present optical communication networks, which solely support classical applications, and future hybrid networks, which will offer both data transmission services as well as QKD-driven secure communications. That will enable long-distance classical-quantum communication at a national scale.