Hybrid Quantum-Classical Communication Networks

点击翻译按钮获取中文摘要

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.