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The laws of physics play a crucial role in the security of quantum key distribution (QKD). This fact has often been misunderstood as if the security of QKD would be based only on the laws of physics. As the experts know well, things are…

Quantum Physics · Physics 2014-12-03 Valerio Scarani , Christian Kurtsiefer

Quantum key distribution (QKD) is a revolutionary cryptography response to the rapidly growing cyberattacks threat posed by quantum computing. Yet, the roadblock limiting the vast expanse of secure quantum communication is the exponential…

There is a big gap between theory and practice in quantum key distribution (QKD) because real devices do not satisfy the assumptions required by the security proofs. Here, we close this gap by introducing a simple and practical…

Quantum Physics · Physics 2021-03-31 Álvaro Navarrete , Margarida Pereira , Marcos Curty , Kiyoshi Tamaki

Quantum key distribution (QKD) protocols aim at allowing two parties to generate a secret shared key. While many QKD protocols have been proven unconditionally secure in theory, practical security analyses of experimental QKD…

Quantum Physics · Physics 2023-07-04 Michel Boyer , Gilles Brassard , Nicolas Godbout , Rotem Liss , Stéphane Virally

A prevalent issue in practical applications of quantum key distribution (QKD) is the emergence of correlations among the emitted signals. Although recent works have proved the security of QKD in the presence of this imperfection, they rest…

It has been widely claimed and believed that many protocols in quantum key distribution, especially the single-photon BB84 protocol, have been proved unconditionally secure at least in principle, for both asymptotic and finite protocols…

Quantum Physics · Physics 2012-07-03 Horace P. Yuen

There is no doubt that quantum key distribution is an excellent result as a science. However, this paper presents a view on quantum key distribution (QKD) wherein QKD may have a difficulty to provide a sufficient security and good…

Quantum Physics · Physics 2014-09-23 Osamu Hirota

We analyze the security and feasibility of a protocol for Quantum Key Distribution (QKD), in a context where only one of the two parties trusts his measurement apparatus. This scenario lies naturally between standard QKD, where both parties…

Quantum Key Distribution (QKD) protocols rely on authenticated classical communication. Typical QKD security proofs are carried out in an idealized setting where authentication is assumed to behave honestly: it never aborts, and all…

Quantum Physics · Physics 2026-01-27 Devashish Tupkary , Shlok Nahar , Ernest Y. -Z. Tan

Quantum key distribution (QKD) promises unconditional security in data communication and is currently being deployed in commercial applications. Nonetheless, before QKD can be widely adopted, it faces a number of important challenges such…

Quantum Physics · Physics 2017-01-24 Eleni Diamanti , Hoi-Kwong Lo , Bing Qi , Zhiliang Yuan

The quantum key distribution (QKD), guaranteed by the principle of quantum physics, is a promising solution for future secure information and communication technology. However, device imperfections compromise the security of real-life QKD…

Quantum Physics · Physics 2022-09-14 Ye Chen , Chunfeng Huang , Zihao Chen , Wenjie He , Chengxian Zhang , Shihai Sun , Kejin Wei

We review the implementation of two QKD protocols (BB84 and B92) keeping in mind that their implementations do not easily satisfy the requirement of use of single photons. We argue that current models do not take into account issues raised…

Cryptography and Security · Computer Science 2011-10-24 Monica Lavale

The security of quantum key distribution (QKD) is quantified by a parameter $\varepsilon>0$, which -- under well-defined physical assumptions -- can be bounded explicitly. This contrasts with computationally secure schemes, where security…

Quantum Physics · Physics 2025-09-18 Carla Ferradini , Martin Sandfuchs , Ramona Wolf , Renato Renner

The performance of quantum key distribution (QKD) is severely limited by multi-photon pulses emitted by laser sources due to the photon-number splitting attack. Coherent-one-way (COW) QKD has been introduced as a promising solution to…

Quantum Physics · Physics 2021-01-06 Javier González-Payo , Róbert Trényi , Weilong Wang , Marcos Curty

In theory, quantum key distribution (QKD) allows secure communications between two parties based on physical laws. However, most of the security proofs of QKD today make unrealistic assumptions and neglect many relevant device…

Quantum Physics · Physics 2019-08-06 Margarida Pereira , Marcos Curty , Kiyoshi Tamaki

Several fundamental issues in establishing security in continuous variable quantum key distribution are discussed, in particular on reverse reconciliation and security under heterodyne attack. It appears difficult to derive quantum…

Quantum Physics · Physics 2016-11-11 Horace P. Yuen

Distributed-phase-reference quantum key distribution stands out for its easy implementation with present day technology. Since many years, a full security proof of these schemes in a realistic setting has been elusive. For the first time,…

Quantum Physics · Physics 2013-07-05 Tobias Moroder , Marcos Curty , Charles Ci Wen Lim , Le Phuc Thinh , Hugo Zbinden , Nicolas Gisin

Typical security proofs for quantum key distribution (QKD) rely on having some model for the devices, with the security guarantees implicitly relying on the values of various parameters of the model, such as dark count rates or detector…

Quantum Physics · Physics 2025-08-22 Ernest Y. -Z. Tan , Shlok Nahar

Quantum key distribution (QKD) promises information-theoretic security based on quantum mechanics, but practical implementations face security vulnerabilities due to device imperfections. Recent advances have separately addressed source and…

Quantum Physics · Physics 2025-07-08 Guillermo Currás-Lorenzo , Margarida Pereira , Shlok Nahar , Devashish Tupkary

We review the current status of security proofs for practical decoy-state Quantum Key Distribution using the BB84 protocol, focusing on optical implementations with weak coherent pulses and threshold photodetectors. The primary aim of this…

Quantum Physics · Physics 2025-05-19 Devashish Tupkary , Ernest Y. -Z. Tan , Shlok Nahar , Lars Kamin , Norbert Lütkenhaus