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Most security proofs of quantum key distribution (QKD) disregard the effect of information leakage from the users' devices, and, thus, do not protect against Trojan-horse attacks (THAs). In a THA, the eavesdropper injects strong light into…

Quantum Physics · Physics 2022-09-12 Álvaro Navarrete , Marcos Curty

Implementations of quantum key distribution (QKD) need vulnerability assessment against loopholes in their optical scheme. Most of the optical attacks involve injecting or receiving extraneous light via the communication channel. An…

Quantum Physics · Physics 2026-05-01 Hao Tan , Mikhail Petrov , Weiyang Zhang , Liying Han , Sheng-Kai Liao , Vadim Makarov , Feihu Xu , Jian-Wei Pan

A highly attenuated laser pulse which gives a weak coherent state is widely used in quantum key distribution (QKD) experiments. A weak coherent state has multi-photon components, which opens up a security loophole to the sophisticated…

Quantum Physics · Physics 2008-08-12 Xiongfeng Ma

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

Quantum key distributions (QKD) systems often rely on polarization of light for encoding, thus limiting the amount of information that can be sent per photon and placing tight bounds on the error that such a system can tolerate. Here we…

Quantum key distribution (QKD) protocol has been proved to provide unconditionally secure key between two remote legitimate users in theory. Key distribution signals are transmitted in a quantum channel which is established by the…

Quantum Physics · Physics 2018-03-14 Yang-Yang Fei , Xiang-Dong Meng , Ming Gao , Hong Wang , Zhi Ma

Quantum key distribution (QKD) enables information-theoretically secure communication against eavesdropping. However, phase instability remains a challenge across many QKD applications, particularly in schemes such as twin-field QKD and…

For secure practical systems, quantum key distribution (QKD) must provide high key rates over long distances. Time-entanglement-based QKD promises to increase the secret key rate and distribution distances compared to other QKD…

Information Theory · Computer Science 2023-03-06 Lara Dolecek , Emina Soljanin

Quantum Key Distribution with the BB84 protocol has been shown to be unconditionally secure even using weak coherent pulses instead of single-photon signals. The distances that can be covered by these methods are limited due to the loss in…

Quantum Physics · Physics 2009-11-10 Marcos Curty , Norbert Lütkenhaus

The security of quantum key distribution (QKD) relies on the Heisenberg uncertainty principle, with which legitimate users are able to estimate information leakage by monitoring the disturbance of the transmitted quantum signals. Normally,…

Quantum Physics · Physics 2017-04-03 Zhen Zhang , Xiao Yuan , Zhu Cao , Xiongfeng Ma

Quantum cryptographic key distribution (QKD) uses extremely faint light pulses to carry quantum information between two parties (Alice and Bob), allowing them to generate a shared, secret cryptographic key. Autocompensating QKD systems…

Quantum Physics · Physics 2009-11-07 Donald S. Bethune , William P. Risk

In real-life implementations of quantum key distribution (QKD), the physical systems with unwanted imperfections would be exploited by an eavesdropper. Based on imperfections in the detectors, detector control attacks have been successfully…

Quantum Physics · Physics 2019-09-25 Yong-Jun Qian , De-Yong He , Shuang Wang , Wei Chen , Zhen-Qiang Yin , Guang-Can Guo , Zheng-Fu Han

Quantum key distribution (QKD) enables two parties to establish a secret key over a potentially hostile channel by exchanging photonic quantum states, relying on the fact that it is impossible for an eavesdropper to tap the quantum channel…

Quantum Physics · Physics 2011-10-24 Jacob Mower , F. N. C. Wong , Jeff H. Shapiro , Dirk Englund

Quantum key distribution (QKD) offers the promise of absolutely secure communications. However, proofs of absolute security often assume perfect implementation from theory to experiment. Thus, existing systems may be prone to insidious…

Quantum Physics · Physics 2014-06-23 Samuel L. Braunstein , Stefano Pirandola

Now that fundamental quantum principles of indeterminacy and measurement have become the basis of new technologies that provide secrecy between two communicating parties, there is a need to provide teaching laboratories that illustrate how…

Quantum Physics · Physics 2021-02-03 Aayam Bista , Baibhav Sharma , Enrique J. Galvez

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

Measurement-device-independent quantum key distribution (MDI-QKD) can eliminate all detector side-channel loopholes and has shown excellent performance in long-distance secret keys sharing. Conventional security proofs, however, require…

Quantum Physics · Physics 2022-02-09 Hua-Jian Ding , Xing-Yu Zhou , Chun-Hui Zhang , Jian Li , Qin Wang

Quantum key distribution (QKD) and quantum message encryption protocols promise a secure way to distribute information while detecting eavesdropping. However, current protocols may suffer from significantly reduced eavesdropping protection…

Quantum Physics · Physics 2025-05-27 Nicholas J. C. Papadopoulos , Kirby Linvill

By employing real-time monitoring of single-photon avalanche photodiodes we demonstrate how two types of practical eavesdropping strategies, the after-gate and time-shift attacks, may be detected. Both attacks are identified with the…

Quantum Physics · Physics 2012-08-03 T. Ferreira da Silva , G. B. Xavier , G. P. Temporão , J. P. von der Weid

In the recent decade, it has been discovered that QKD systems are extremely vulnerable to side-channel attacks. In particular, by exploiting the internal working knowledge of practical detectors, it is possible to bring them to an operating…

Quantum Physics · Physics 2015-02-02 Charles Ci Wen Lim , Nino Walenta , Matthieu Legre , Nicolas Gisin , Hugo Zbinden