Distributing Secret Keys with Quantum Continuous Variables: Principle, Security and Implementations

TL;DR

This paper reviews continuous-variable quantum key distribution, highlighting its principles, security, experimental progress, and practical advantages over qubit-based methods, emphasizing its potential for real-world secure communication.

Contribution

It provides a comprehensive overview of continuous-variable quantum key distribution protocols, security analysis, and recent experimental advancements, emphasizing practical implementation benefits.

Findings

CV-QKD protocols based on coherent states are secure and practical.

Experimental implementations have demonstrated real-world viability.

Side-channel attacks are a key consideration in security assessments.

Abstract

The ability to distribute secret keys between two parties with information-theoretic security, that is, regardless of the capacities of a malevolent eavesdropper, is one of the most celebrated results in the field of quantum information processing and communication. Indeed, quantum key distribution illustrates the power of encoding information on the quantum properties of light and has far reaching implications in high-security applications. Today, quantum key distribution systems operate in real-world conditions and are commercially available. As with most quantum information protocols, quantum key distribution was first designed for qubits, the individual quanta of information. However, the use of quantum continuous variables for this task presents important advantages with respect to qubit based protocols, in particular from a practical point of view, since it allows for simple implementations that require only standard telecommunication technology. In this review article, we describe the principle of continuous-variable quantum key distribution, focusing in particular on protocols based on coherent states. We discuss the security of these protocols and report on the state-of-the-art in experimental implementations, including the issue of side-channel attacks. We conclude with promising perspectives in this research field.