Radioelectronics Nanosystems Information Technologies

Key Features of Continuous-Variable Quantum Key Distribution Protocols

Evgenii V. Burlakov, Alexander V. Korobov

Published Apr 24, 2024• 2 citations

Abstract

The key features of continuous variables quantum key distribution protocols are considered in the paper. The motivation for studying and developing methods of quantum cryptography is substantiated. The main aspects inherent to continuous-variable protocols are highlighted, and they are classified based on various characteristics, peculiarities, and implementation variants. A detailed examination of a protocol example with discrete modulation and signal registration through balanced homodyne detection is provided. A classification of attacks on the quantum protocol is presented. A general overview of post-processing methods is given. The role of noise is indicated, and approaches to assessing the level of security applicable to continuous-variable protocols are discussed. In conclusion, the main conclusions regarding the current status of this problem are presented, and aspects requiring further study are identified.

DOI: 10.17725/j.rensit.2024.16.255

Related papers

Theoretical development of discrete-modulated continuous-variable quantum key distribution

Wen‐Bo Liu, Chenlong Li, Zhiping Liu +3 more

Continuous-variable quantum key distribution offers simple, stable and easy-to-implement key distribution systems. The discrete modulation scheme further reduces the technical difficulty. The main regret is that the security of discrete modulation schemes has not been sufficiently demonstrated. Schemes with different signal state distributions use various physical conditions to obtain the key rate formula, resulting in different security levels, computation complexities and implementation difficulties. Therefore, a relatively systematic and logically consistent security proof against most general attacks is worth exploring. On the other hand, extending the discrete modulation scheme and its variants to different applications, such as satellite-to-earth communication, can further activate and advance this field. Here, we briefly review the achievements that have been made in discrete-modulated continuous-variable quantum key distribution, and openly discuss some issues worthy of further research.

Frontiers in Quantum Science and TechnologyOct 13, 20228 citations

Security analysis of Quantum Key Distribution

Fernández Raventós, Núria

Quantum Key Distribution (QKD) provides a method for securely sharing a secret key between two distant parties, Alice and Bob, by leveraging the principles of quantum mechanics. This thesis focuses on Continuous-Variable (CV) QKD, a variant of QKD where information is encoded in the quadrature components of coherent light states, allowing for efficient and cost-effective detection using homodyne or heterodyne receivers. The thesis is divided into three main parts: an introduction to quantum cryptography concepts, the presentation of a CV-QKD protocol, and a detailed security proof of the protocol against different types of attacks. The security proof considers both finite and infinite symbol transmission and tackles various eavesdropping attacks, including individual, collective, and coherent attacks. The use of Gaussian states and operations provides a promising approach to enhance QKD security, particularly in the context of practical quantum cryptography. The final sections provide a mathematical framework for the optimization of secure key rates and strategies for addressing the photon-number cutoff assumption in practical implementations.

Oct 24, 20240 citations

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

Yichen Zhang, Yiming Bian, Zhengyu Li +2 more

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 progresses 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.

arXiv:2310.04831Applied Physics ReviewsMar 1, 2024198 citations

Continuous-Variable Quantum Key Distribution

Frédéric Grosshans, A. Acín, Nicolas J. Cerf

Quantum key distribution is a technique in which secret key bits are encoded into quantum states which are transmitted over a quantum channel, e.g. an optical link, so that the security is guaranteed by the laws of quantum physics. Most experimental realizations to date have relied on discrete protocols, involving ideally single-photons states (or, in practice, strongly attenuated light pulses) as well as single-photon detectors. In this chapter, we present an overview of the recent continuous-variable quantum cryptosystems, which instead rely on continuously-modulated Gaussian states (e.g. coherent states) and homodyne detection. The series of security proofs of these protocols against increasingly powerful attacks will be reviewed. A particular emphasis will be put on the op-timality of Gaussian attacks in this context, which holds provided that the second-order moments of the relevant variables are monitored.

IMPERIAL COLLEGE PRESS eBooksFeb 1, 20077 citations

Strategies of Legitimate Parties and an Eavesdropper for Discretely Modulated Continuous-Variables Quantum Key Distribution Protocols

M. Facão, Vitor Ferreira, Alexandre Marques +2 more

Discretely modulated continuous-variables quantum key distribution (CV-QKD) protocols are usually proposed with phase modulated coherent states being sent by Alice and simple homodyne detection on the Bob side and, in the majority of the studies, their security is analyzed assuming that for low photon number the protocols are similar to a Gaussian modulated CV-QKD. Here we discuss other detection techniques such as double homodyne, consider classical attacks and find practical strategies for the legitimate parties to reach the security limits predicted by the Gaussian modulated CV-QKD.

International Conference on Transparent Optical NetworksJul 1, 20190 citations

Finite-size security of continuous-variable quantum key distribution with digital signal processing

Takaya Matsuura, Kento Maeda, Toshihiko Sasaki +1 more

Abstract In comparison to conventional discrete-variable (DV) quantum key distribution (QKD), continuous-variable (CV) QKD with homodyne/heterodyne measurements has distinct advantages of lower-cost implementation and affinity to wavelength division multiplexing. On the other hand, its continuous nature makes it harder to accommodate to practical signal processing, which is always discretized, leading to lack of complete security proofs so far. Here we propose a tight and robust method of estimating fidelity of an optical pulse to a coherent state via heterodyne measurements. We then construct a binary phase modulated CV-QKD protocol and prove its security in the finite-key-size regime against general coherent attacks, based on proof techniques of DV QKD. Such a complete security proof is indispensable for exploiting the benefits of CV QKD.

Jan 1, 202157 citations