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Security of quantum key distribution against sophisticated attacks is among the most important issues in quantum information theory. In this work we prove security against a very important class of attacks called collective attacks (under a…

Quantum Physics · Physics 2007-05-23 Eli Biham , Michel Boyer , Gilles Brassard , Jeroen van de Graaf , Tal Mor

In this thesis we study the finite-size analysis of two continuous-variables quantum key distribution schemes. The first one is the one-way protocol using Gaussian modulation of thermal states and the other is the…

Quantum Physics · Physics 2019-06-13 Panagiotis Papanastasiou

Quantum Key Distribution (QKD) schemes are key exchange protocols based on the physical properties of quantum channels. They avoid the computational-hardness assumptions that underlie the security of classical key exchange.…

Quantum Physics · Physics 2025-12-19 Arpan Akash Ray , Boris Skoric

Quantum digital signatures (QDSs), which utilize correlated bit strings among sender and recipients, guarantee the authenticity, integrity, and nonrepudiation of classical messages based on quantum laws. Continuous-variable (CV) quantum…

Quantum Physics · Physics 2024-11-25 Yi-Fan Zhang , Wen-Bo Liu , Bing-Hong Li , Hua-Lei Yin , Zeng-Bing Chen

We present the optimal collective attack on a Quantum Key Distribution (QKD) protocol in the "device-independent" security scenario, where no assumptions are made about the way the QKD devices work or on what quantum system they operate.…

Quantum Physics · Physics 2007-10-22 Antonio Acin , Nicolas Brunner , Nicolas Gisin , Serge Massar , Stefano Pironio , Valerio Scarani

Quantum Key Distribution (QKD) in principle offers unconditional security based on the laws of physics. Continuous variable (CV) quantum key distribution has the potential for high-key-rate and low-cost implementations using standard…

Quantum Physics · Physics 2021-10-19 Chenyang Li , Li Qian , Hoi-Kwong Lo

Modern security proofs of quantum key distribution (QKD) must take finite-size effects and composable aspects into consideration. This is also the case for continuous-variable (CV) protocols which are based on the transmission and detection…

Quantum Physics · Physics 2025-11-27 Stefano Pirandola , Panagiotis Papanastasiou

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…

Quantum Physics · Physics 2021-01-18 Takaya Matsuura , Kento Maeda , Toshihiko Sasaki , Masato Koashi

Quantum Key Distribution (QKD) offers unconditional security in principle. Many QKD protocols have been proposed and demonstrated to ensure secure communication between two authenticated users. Continuous variable (CV) QKD offers many…

Security of practical continuous-variable quantum key distribution is addressed and a security analysis framework, which does not rely on phase-space symmetries of signal states and correlations, is developed. In a general…

Quantum Physics · Physics 2019-08-06 Vladyslav C. Usenko

We calculate eavesdropper's optimal information on raw bits in Bennett-Brassard 1984 quantum key distribution (BB84 QKD) and six-state scheme in coherent attacks, using a formula by Lo and Chau [Science 283 (1999) 2050] with single photon…

Quantum Physics · Physics 2009-11-06 W. Y. Hwang , D. Ahn , S. W. Hwang

The possibility of using squeezed states in the recently suggested unidimensional continuous-variable quantum key distribution based on a single quadrature modulation is addressed. It is shown that squeezing of the signal states expands the…

Quantum Physics · Physics 2018-09-26 Vladyslav C. Usenko

In a continuous-variable quantum key distribution (CVQKD) system, the information is conveyed by coherent state carriers. The quantum continuous variables are sent through a quantum channel, where the presence of the eavesdropper adds a…

Quantum Physics · Physics 2015-06-17 Laszlo Gyongyosi

We have developed a method to calculate a secret key rate of a continuous-variable quantum-key-distribution scheme using four coherent states and postselection for a general model of Gaussian attacks. We assume that the transmission line…

Quantum Physics · Physics 2018-10-30 Ryo Namiki , Akira Kitagawa , Takuya Hirano

Quantum Key Distribution (QKD) is a cutting-edge communication method that enables secure communication between two parties. Continuous-variable QKD (CV-QKD) is a promising approach to QKD that has several advantages over traditional…

Quantum Physics · Physics 2023-05-26 Andres Ruiz-Chamorro , Daniel Cano , Aida Garcia-Callejo , Veronica Fernandez

This paper proposes a multi-mode Gaussian modulated continuous variable quantum key distribution (CV-QKD) scheme able to operate at high bandwidth despite using conventional noisy, coherent detectors. We demonstrate enhancement in shotnoise…

Quantum Physics · Physics 2019-07-24 Rupesh Kumar , Xinke Tang , Adrian Wonfor , Richard Penty , Ian White

Many papers proved the security of quantum key distribution (QKD) system, in the asymptotic framework. The degree of the security has not been discussed in the finite coding-length framework, sufficiently. However, to guarantee any…

Quantum Physics · Physics 2009-11-13 Masahito Hayashi

A numerical security proof technique is used to analyse the security of continuous-variable quantum key distribution (CV-QKD) protocols with phase-shift keying modulation against collective attacks in the asymptotic limit. We argue why it…

Quantum Physics · Physics 2022-10-18 Florian Kanitschar , Christoph Pacher

The security proof of continuous variable quantum key distribution(CV QKD) based on two assumptions that the eavesdropper can neither act on the local oscillator nor control Bob's beam splitter. These assumptions maybe invalid in practice…

Quantum Physics · Physics 2013-05-14 Jing-Zheng Huang , Zhen-Qiang Yin , Shuang Wang , Hong-Wei Li , Wei Chen , Guan-Can Guo , Zheng-Fu Han

We propose a long-distance continuous-variable quantum key distribution (CVQKD) with four-state protocol using non-Gaussian state-discrimination detection. A photon subtraction operation, which is deployed at the transmitter, is used for…

Quantum Physics · Physics 2018-07-23 Qin Liao , Ying Guo , Duang Huang , Peng Huang , Guihua Zeng