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We report on the first real-time implementation of a quantum key distribution (QKD) system using entangled photon pairs that are sent over two free-space optical telescope links. The entangled photon pairs are produced with a type-II…

Quantum Physics · Physics 2012-10-25 C. Erven , C. Couteau , R. Laflamme , G. Weihs

Quantum key distribution (QKD) enables information-theoretic secure communication, yet its ultimate tolerance to noise and achievable transmission distance remain fundamentally constrained. We establish the maximum quantum bit error rate…

Quantum Physics · Physics 2026-02-27 Stefano Pirandola

Twin-field quantum key distribution (TFQKD), using single-photon-type interference, offers a way to exceed the rate-distance limit without quantum repeaters. However, it still suffers from the photon losses and dark counts, which impose an…

Quantum Physics · Physics 2021-11-09 Bing-Hong Li , Yuan-Mei Xie , Zhao Li , Chen-Xun Weng , Chen-Long Li , Hua-Lei Yin , Zeng-Bing Chen

Quantum key distribution is a way to distribute secret keys to distant users with information theoretic security and key rates suitable for real-world applications. Its rate-distance figure, however, is limited by the natural loss of the…

Quantum Physics · Physics 2018-09-12 Kiyoshi Tamaki , Hoi-Kwong Lo , Wenyuan Wang , Marco Lucamarini

Quantum key distribution (QKD) theoretically offers information-theoretic security. The prevailing approach is the prepare-and-measure BB84 protocol, which implements QKD using conventional laser rather than single-photon source via the…

Quantum Physics · Physics 2026-05-20 Rong-Zheng Liu , Hua-Lei Yin

Twin-field quantum key distribution (TF-QKD) has emerged as a promising solution for practical quantum communication over long-haul fiber. However, previous demonstrations on TF-QKD require the phase locking technique to coherently control…

Quantum key distribution (QKD) leverages the principles of quantum mechanics to exchange a secret key between two parties. Despite its promising features, QKD also faces several practical challenges such as transmission loss, noise in…

We report the first real world implementation of a Quantum Key Distribution (QKD) system over a 43dB-loss transmission line in the Swisscom fibre optic network. The QKD system is capable of continuous and autonomous operation and uses the…

Large-scale quantum communication networks are still a huge challenge due to the rate-distance limit of quantum key distribution (QKD). Recently, twin-field (TF) QKD has been proposed to overcome this limit. Here, we prove that…

Quantum Physics · Physics 2019-11-21 Hua-Lei Yin , Zeng-Bing Chen

We address the question of the implementation of long-distance device-independent quantum key distribution (DI QKD) by proposing two experimentally viable schemes. Those schemes only use spontaneous parametric down-conversion (SPDC) sources…

Quantum key distribution (QKD) together with one time pad encoding can provide information-theoretical security for communication. Currently, though QKD has been widely deployed in many metropolitan fiber networks, its implementation in a…

Quantum Physics · Physics 2018-09-10 Qiang Zhang , Feihu Xu , Yu-Ao Chen , Cheng-Zhi Peng , Jian-Wei Pan

Building scalable and secure quantum networks requires advanced quantum key distribution (QKD) protocols that support multi-user connectivity. Continuous-variable (CV) measurement-device-independent (MDI) QKD, which eliminates all detector…

Quantum Physics · Physics 2024-10-18 Adnan A. E. Hajomer , Ulrik L Andersen , Tobias Gehring

We present a measurement-device-independent quantum key distribution (MDI-QKD) using single photons in a linear superposition of three orthogonal time-bin states, for generating the key. The orthogonal states correspond to three distinct…

Quantum Physics · Physics 2021-02-24 Shashank Kumar Ranu , Anil Prabhakar , Prabha Mandayam

Differential-phase-shift (DPS) quantum key distribution (QKD) is one of the major QKD protocols that can be implemented with a simple setup using a laser source and a passive detection unit. Recently, an information-theoretic security proof…

Quantum Physics · Physics 2023-06-01 Akihiro Mizutani , Yuki Takeuchi , Kiyoshi Tamaki

Decoy State Quantum Key Distribution (QKD), being capable of beating PNS attack and uncon- ditionally secure, have become an attractive one recently. But, in many QKD systems, disturbances of transmission channel make quantum bit error rate…

Quantum Physics · Physics 2009-11-13 Zhen-Qiang Yin , Zheng-Fu Han , Wei Chen , Fang-Xing Xu , Qing-Lin Wu , Guang-Can Guo

Quantum key distribution (QKD) enables unconditionally secure communication guaranteed by the laws of physics. The last decades have seen tremendous efforts in making this technology feasible under real-life conditions, with implementations…

Quantum Physics · Physics 2021-04-14 Sebastian Philipp Neumann , Domenico Ribezzo , Martin Bohmann , Rupert Ursin

Quantum key distribution (QKD) is a cryptographic technique that uses quantum mechanical principles to enable secure key exchange. Practical deployment of QKD requires robust, cost-effective systems that can operate in challenging field…

Quantum Physics · Physics 2026-04-07 Rui Guan , Jingchun Yu , Zhaoyun Li , Hongbo Xie , Yuxing Wei , Sen Li , Jing Wen , Xiaodong Liang , Yanwei Li , Kejin Wei

There are two main factors limiting the performance of quantum key distribution --- channel transmission loss and noise. Previously, a linear bound was believed to put an upper limit on the rate-transmittance performance. Remarkably, the…

Quantum Physics · Physics 2020-07-01 Pei Zeng , Weijie Wu , Xiongfeng Ma

The security of conventional cryptography systems is threatened in the forthcoming era of quantum computers. Quantum key distribution (QKD) features fundamentally proven security and offers a promising option for quantum-proof cryptography…

Quantum Physics · Physics 2017-11-29 Nurul T. Islam , Charles Ci Wen Lim , Clinton Cahall , Jungsang Kim , Daniel J. Gauthier

Quantum key distribution (QKD) promises provably secure communications. In order to improve the secret key rate, combining a biased basis choice with the decoy-state method is proposed. Concomitantly, there is a basis-independent detection…

Quantum Physics · Physics 2021-08-11 Hua-Lei Yin , Peng Liu , Wei-Wei Dai , Zhao-Hui Ci , Jie Gu , Tian Gao , Qiang-Wei Wang , Zi-Yao Shen