We provide an overview of the state-of-the-art in continuous-variable quantum key distribution, including long-distance experiments and the analysis of the practical security of such implementations. We also discuss exciting perspectives in the field.
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.
The review examines the essential characteristics of continuous-variable quantum key distribution protocols. In these protocols, information is encoded into the complex amplitude of the optical field, which can have a continuous range of values, unlike a qubit. An advantage over many other quantum key distribution protocols is provided by the fact that the practical implementation of these protocols does not require sources and single-photon detectors. Additionally, they offer a relatively high rate of secret key generation. However, continuous-variable protocols require a specific analysis of secrecy and special consideration for the influence of noise that may arise during practical implementation. This presents a broad area for further research.
Quantum key distribution enables unconditionally secure key distribution between two legitimate users. The information-theoretic security is guaranteed by the fundamental laws of quantum physics. Initially, the quantum key distribution protocol was proposed based on the qubits. Later on, it was found that quantum continuous variables can also be exploited for this target. The continuous variable quantum key distribution can build upon standard telecommunication technology and exhibits a higher secret key rate per pulse at a relatively short distance due to the possibility of encoding more than 1 bit per pulse. In this article, we review the current status of the continuous variable quantum key distribution research, including its basic principle, experimental implementations, security and future directions; the experimental progress in this field made by our group is also presented.
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.