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Ideal quantum key distribution (QKD) protocols call for a source that emits single photon signals, but the sources used in typical practical realizations emit weak coherent states instead. A weak coherent state may contain more than one…

Quantum Physics · Physics 2007-05-23 Hoi-Kwong Lo , John Preskill

The postselection technique is an important proof technique for proving the security of quantum key distribution protocols against coherent attacks. In this work, we go through multiple steps to rigorously apply the postselection technique…

Quantum Physics · Physics 2024-10-31 Shlok Nahar , Devashish Tupkary , Yuming Zhao , Norbert Lütkenhaus , Ernest Y. -Z. Tan

Most continuous-variable quantum key distribution schemes are based on the Gaussian modulation of coherent states followed by continuous quadrature detection using homodyne detectors. In all previous schemes, the Gaussian modulation has…

Quantum Physics · Physics 2016-09-06 Tobias Gehring , Christian S. Jacobsen , Ulrik L. Andersen

Efficiency is a key issue in any real implementation of a cryptographic protocol since the physical resources are not unlimited. We will first show that Quantum Key Distribution is possible with an "Entanglement based" scheme with NPPT…

Quantum Physics · Physics 2015-03-17 Carles Rodó

We have designed and realized a prototype that implements a continuous-variable quantum key distribution protocol based on coherent states and reverse reconciliation. The system uses time and polarization multiplexing for optimal…

Quantum key distribution has emerged as a promising solution for constructing secure communication networks, offering information-theoretic security guaranteed by the principles of quantum mechanics. One of the most advanced quantum key…

Quantum Physics · Physics 2024-08-30 Yizhi Huang , Zhenyu Du , Xiongfeng Ma

Quantum Key Distribution or QKD provides symmetric key distribution using the quantum mechanics/channels with new security properties. The security of QKD relies on the difficulty of the quantum state discrimination problem. We discover…

Quantum Physics · Physics 2021-02-23 Yaroslav Balytskyi , Manohar Raavi , Anatoliy Pinchuk , Sang-Yoon Chang

Quantum technology can enable secure communication for cryptography purposes using quantum key distribution. Quantum key distribution protocols provide a secret key between two users with security guaranteed by the laws of quantum…

Quantum Physics · Physics 2024-10-11 Venkat Abhignan , Abhishek Jamunkar , Gokul Nair , Mohit Mittal , Megha Shrivastava

Practical quantum key distribution (QKD) protocols require a finite-size security proof. The phase error correction (PEC) approach is one of the general strategies for security analyses that has successfully proved finite-size security for…

Quantum Physics · Physics 2026-05-15 Takaya Matsuura , Shinichiro Yamano , Yui Kuramochi , Toshihiko Sasaki , Masato Koashi

We propose efficient-phase-encoding protocols for continuous-variable quantum key distribution using coherent states and postselection. By these phase encodings, the probability of basis mismatch is reduced and total efficiency is…

Quantum Physics · Physics 2008-09-29 Ryo Namiki , Takuya Hirano

Recently, we have shown the advantages of two-way quantum communications in continuous variable quantum cryptography. Thanks to this new approach, two honest users can achieve a non-trivial security enhancement as long as the Gaussian…

Quantum Physics · Physics 2008-09-18 Stefano Pirandola , Stefano Mancini , Seth Lloyd , Samuel L. Braunstein

We extend the security proof for continuous variable quantum key distribution protocols using post selection to account for arbitrary eavesdropping attacks by employing the concept of an equivalent protocol where the post-selection is…

Quantum Physics · Physics 2013-03-08 Nathan Walk , Thomas Symul , Ping Koy Lam , Timothy C. Ralph

As quantum key distribution becomes a mature technology, it appears clearly that some assumptions made in the security proofs cannot be justified in practical implementations. This might open the door to possible side-channel attacks. We…

Quantum Physics · Physics 2015-06-05 Paul Jouguet , Sébastien Kunz-Jacques , Eleni Diamanti , Anthony Leverrier

We investigate the performance of Gaussianmodulated coherent-state QKD protocols in the presence of canonical attacks, which are collective Gaussian attacks resulting in Gaussian channels described by one of the possible canonical forms. We…

Quantum Physics · Physics 2021-09-07 Panagiotis Papanastasiou , Carlo Ottaviani , Stefano Pirandola

We derive a proof of security for the Differential Phase Shift Quantum Key Distribution (DPSQKD) protocol under the assumption that Eve is restricted to individual attacks. The security proof is derived by bounding the average collision…

Quantum Physics · Physics 2009-11-11 Edo Waks , Hiroki Takesue , Yoshihisa Yamamoto

Secure quantum key distribution with multimode Gaussian entangled states and multimode homodyne detectors is proposed. In general the multimode character of both the sources of entanglement and the homodyne detectors can cause a security…

Quantum Physics · Physics 2014-12-19 Vladyslav C. Usenko , Laszlo Ruppert , Radim Filip

We consider the security of continuous-variable quantum key distribution using thermal (or noisy) Gaussian resource states. Specifically, we analyze this against collective Gaussian attacks using direct and reverse reconciliation where both…

Quantum Physics · Physics 2013-04-17 Christian Weedbrook , Stefano Pirandola , Timothy C. Ralph

We consider two-way continuous-variable quantum key distribution, studying its security against general eavesdropping strategies. Assuming the asymptotic limit of many signals exchanged, we prove that two-way Gaussian protocols are immune…

Quantum Physics · Physics 2017-05-09 Carlo Ottaviani , Stefano Pirandola

A general study of arbitrary finite-size coherent attacks against continuous-variable quantum cryptographic schemes is presented. It is shown that, if the size of the blocks that can be coherently attacked by an eavesdropper is fixed and…

Quantum Physics · Physics 2007-05-23 Frederic Grosshans , Nicolas J. Cerf

A cryptographic algorithm is proposed based on fully quantum mechanical keys and ciphers. Encryption and decryption are carried out via an appropriate measurement process on entangled states as governed by a quantum mechanical, asymmetrical…

Quantum Physics · Physics 2007-05-23 Guihua Zeng , Carlos Saavedra , Christoph H. Keitel