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Quantum key distribution (QKD) promises everlasting security based on the laws of physics. Most common protocols are grouped into two distinct categories based on the degrees of freedom used to carry information, which can be either…

Quantum Physics · Physics 2024-02-28 Jasminder S. Sidhu , Rocco Maggi , Saverio Pascazio , Cosmo Lupo

Protecting secure random key from eavesdropping in quantum key distribution protocols has been well developed. In this letter, we further study how to detect and eliminate eavesdropping on the random base string in such protocols. The…

Quantum Physics · Physics 2007-06-27 Kai Wen , Fu Guo Deng , Gui Lu Long

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…

Error filtration is a method for encoding the quantum state of a single particle into a higher dimensional Hilbert space in such a way that it becomes less sensitive to phase noise. We experimentally demonstrate this method by distributing…

Quantum Physics · Physics 2007-05-23 L. P. Lamoureux , E. Brainis , N. Cerf , Ph. Emplit , M. Haelterman , S. Massar

This paper reports a variant of the three-stage quantum cryptography protocol which can be used in low intensity laser output regimes. The variant, which tracks the intensity of the laser beam at the intermediate stages, makes the task of…

Quantum Physics · Physics 2013-10-15 Subhash Kak , Yuhua Chen , Pramode Verma

We describe how to modify the BB84 protocol for quantum cryptography in order to make it deterministic. We study both theoretical and experimental aspects of this issue, showing that the new scheme is as secure as the old one, more…

Quantum Physics · Physics 2007-07-27 M. Lucamarini , J. S. Shaari , M. R. B. Wahiddin

We consider the Bennett-Brassard cryptographic scheme, which uses two conjugate quantum bases. An eavesdropper who attempts to obtain information on qubits sent in one of the bases causes a disturbance to qubits sent in the other basis. We…

Quantum Physics · Physics 2007-05-23 Christopher A. Fuchs , Nicolas Gisin , Robert B. Griffiths , Chi-Sheng Niu , Asher Peres

We present the results of a linear optics photonic implementation of a quantum circuit that simulates a phase covariant cloner, by using two different degrees of freedom of a single photon. We experimentally simulate the action of two…

Quantum Physics · Physics 2017-12-04 Laura T. Knoll , Ignacio H. López Grande , Miguel A. Larotonda

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

This is a study of the security of the Coherent One-Way (COW) protocol for quantum cryptography, proposed recently as a simple and fast experimental scheme. In the zero-error regime, the eavesdropper Eve can only take advantage of the…

Quantum Physics · Physics 2008-02-05 Cyril Branciard , Nicolas Gisin , Norbert Lutkenhaus , Valerio Scarani

Using polarization-entangled photons from spontaneous parametric downconversion, we have implemented Ekert's quantum cryptography protocol. The near-perfect correlations of the photons allow the sharing of a secret key between two parties.…

Quantum Physics · Physics 2009-10-31 D. S. Naik , C. G. Peterson , A. G. White , A. J. Berglund , P. G. Kwiat

All the currently available unconditional security proofs on quantum key distribution, in particular for the BB84 protocol and its variants including continuous-variable ones, are invalid or incomplete at many points. In this paper we…

Quantum Physics · Physics 2013-10-23 Horace P. Yuen

Quantum key distribution (QKD) provides means for unconditional secure key transmission between two distant parties. However, in practical implementations, it suffers from quantum hacking due to device imperfections. Here we propose a…

Quantum Physics · Physics 2014-07-16 Shi-Hai Sun , Mu-Sheng Jiang , Xiang-Chun Ma , Chun-Yan Li , Lin-Mei Liang

Quantum cryptography remains a topic of enduring scientific and educational interest. Here, we present a clear and accessible framework for exploring the six-state quantum key distribution protocol, an enhanced three-basis extension of the…

Quantum Physics · Physics 2025-11-18 Sara P. Gandelman , Georgi Gary Rozenman

We present a finite-size security proof of the decoy-state BB84 QKD protocol against coherent attacks, using entropic uncertainty relations, for imperfect detectors. We apply this result to the case of detectors with imperfectly…

Quantum Physics · Physics 2025-12-16 Devashish Tupkary , Shlok Nahar , Pulkit Sinha , Norbert Lütkenhaus

A communication protocol based on a Gaussian modulation of squeezed states in a single quadrature and measured via homodyne detection can completely eliminate information leakage to an eavesdropper in a pure-loss channel. However, the…

Quantum Physics · Physics 2021-07-21 Matthew S. Winnel , Nedasadat Hosseinidehaj , Timothy C. Ralph

The no-cloning theorem forbids the creation of identical copies of qubits, thereby imposing strong limitations on quantum technologies. A recently-proposed protocol, encrypted cloning, showed, however, that the creation of perfect clones is…

Since, in general, non-orthogonal states cannot be cloned, any eavesdropping attempt in a Quantum Communication scheme using non-orthogonal states as carriers of information introduces some errors in the transmission, leading to the…

Discrete-modulated continuous-variable quantum key distribution offers a pragmatic solution, greatly simplifying experimental procedures while retaining robust integration with classical optical communication. Theoretical analyses have…

Quantum Physics · Physics 2024-07-31 Mingze Wu , Junhui Li , Bingjie Xu , Song Yu , Yichen Zhang

It has been found that the signal can be encoded in the choice of the measurement basis of one of the communicating parties, while the outcomes of the measurement are irrelevant for the communication and therefore may be discarded. The…

Quantum Physics · Physics 2015-06-17 Dong Xie , An Min Wang