Continuous-variable quantum key distribution system: past, present, and future

TL;DR

This review covers the development, current state, and future prospects of continuous-variable quantum key distribution systems, emphasizing protocols based on coherent states and their transition from lab experiments to real-world applications.

Contribution

It provides a comprehensive overview of theoretical protocols, security status, system implementations, and future technological advancements in continuous-variable quantum key distribution.

Findings

Protocols are moving from proof-of-principle to in-field implementations

Advances include digital techniques, system on chip, and point-to-multipoint systems

Practical security considerations are addressed

Abstract

Quantum key distribution provides secure keys with information-theoretic security ensured by the principle of quantum mechanics. The continuous-variable version of quantum key distribution using coherent states offers the advantages of its compatibility with telecom industry, e.g., using commercial laser and homodyne detector, is now going through a booming period. In this review article, we describe the principle of continuous-variable quantum key distribution system, focus on protocols based on coherent states, whose systems are gradually moving from proof-of-principle lab demonstrations to in-field implementations and technological prototypes. We start by reviewing the theoretical protocols and the current security status of these protocols. Then, we discuss the system structure, the key module, and the mainstream system implementations. The advanced progress for future applications are discussed, including the digital techniques, system on chip and point-to-multipoint system. Finally, we discuss the practical security of the system and conclude with promising perspectives in this research field.