arXiv subjects

Yang-Guang Shan

Publications and source records attributed to Yang-Guang Shan.

7 recordsLinked to original sources

arXiv2026

Relativistic Position Verification with Coherent States

Determining the position of an entity is a fundamental prerequisite for nearly all activities. Classical means, however, have been proven incapable of providing secure position verification, meaning that a prover can mislead verifiers about its actual position. In this work, we propose and experimentally realize a secure position-verification protocol that leverages quantum optics and relativity within an information-theoretic framework. Using phase-randomized weak coherent states, two verifiers separated by 2 km securely verify the prover's position with an accuracy better than 75 meters. These results establish secure position-based authentication as a practical possibility, paving the way for applications in financial transactions, disaster response, and authenticated secure communications.

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arXiv2025

Side-channel-secure quantum key distribution with correlated sources

Quantum key distribution (QKD) offers theoretical security guarantees for sharing secure key, but its practical systems face challenges due to the imperfections of devices. Widespread quantum state preparation imperfections, such as correlations between multiple rounds, significantly undermine the real-world security of QKD. In this paper, we propose a protocol that is immune to almost all kinds of state-preparation imperfections over multiple correlated rounds arising from both encoding and unknown non-encoding dimensions. The protocol relies only on three assumptions: the imperfect encoding produces unknown product states rather than entangled ones, a lower bound on the vacuum components is known, and the correlation has a finite range. The proposed protocol is also measurement-device-independent, ensuring high security at both the source and measurement sides. We provide the finite-key security analysis against coherent attacks and conduct numerical simulations to see the performance. The results show that for small correlation ranges, the protocol achieves excellent performance with a maximal transmission loss exceeding 60 dB (>300 km in standard fiber). Even for extreme cases, where one encoding affects up to 500 neighboring rounds, the protocol can still generate secret keys over a 10 dB-loss channel.

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arXiv2025

Secure quantum key distribution against correlated leakage source

Quantum key distribution (QKD) provides information theoretic security based on quantum mechanics, however, its practical deployment is challenged by imperfections of source devices. Among various source loopholes, correlations between transmitted pulses pose a significant yet underexplored security risk, potentially compromising QKD's theoretical guarantees. In this work, we propose a security analysis framework for QKD under correlations, enabling finite-key analysis for the first time by extending and rearranging QKD rounds and leveraging the generalized chain rule. Based on this framework, and inspired by the idea of side-channel-secure QKD, we develop a secure QKD against correlated leakage source only need the characterization of correlation range and the lower bound on the vacuum component of the prepared states. Additionally, our framework can be extended to other QKD protocols, offering a general approach to consider correlation induced security vulnerabilities. The simulation results demonstrate the effectiveness of our protocol and its significantly superior tolerance to imperfect parameters compared to existing protocols. This work provides a crucial step toward closing security loopholes in QKD, enhancing its practicality, and ensuring long-distance,high-performance secure communication under real-world constraints.

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arXiv2024

Improved postselection security analysis of phase error estimation in quantum key distribution

Quantum key distribution (QKD) enables the generation of secure keys between two distant users. Security proof of QKD against general coherent attacks is challenging, while the one against collective attacks is much easier. As an effective and general solution, the postselection method tries to extend security analyses of collective attacks to be against coherent attacks. However, it gives a bad performance. To overcome this drawback, instead of directly calculating key rate by postselection method, we propose a method correlating the failure probabilities of phase error estimation against collective and coherent attacks, enabling the use of the independent and identically distributed assumption in parameter estimation against coherent attacks. Then the key rate can be obtained by uncertainty relation of entropy. Our method can be applied to various QKD protocols, providing better performance compared with the traditional postselection method. For instance, we give the finite-key analyses of the side-channel-secure (SCS) QKD and the no-phase-postselection (NPP) twin-field (TF) QKD to show their performance improvements with the proposed method.

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arXiv2024

Sending-or-not-sending quantum key distribution with phase postselection

Quantum key distribution (QKD) could help to share secure key between two distant peers. In recent years, twin-field (TF) QKD has been widely investigated because of its long transmission distance. One of the popular variants of TF QKD is sending-or-not-sending (SNS) QKD, which has been experimentally verified to realize 1000-km level fibre key distribution. In this article, the authors introduce phase postselection into the SNS protocol. With this modification, the probability of selecting "sending" can be substantially improved. The numerical simulation shows that the transmission distance can be improved both with and without the actively odd-parity pairing method. With discrete phase randomization, the variant can have both a larger key rate and a longer distance.

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arXiv2023

Precise Phase Error Rate Analysis for Quantum Key Distribution with Phase Postselection

Quantum key distribution (QKD) stands as a pioneering method for establishing information-theoretically secure communication channels by utilizing the principles of quantum mechanics. In the security proof of QKD, the phase error rate serves as a critical indicator of information leakage and directly influences the security of the shared key bits between communicating parties, Alice and Bob. In estimating the upper bound of the phase error rate, phase randomization and subsequent postselection mechanisms serve pivotal roles across numerous QKD protocols. Here we make a precise phase error rate analysis for QKD protocols with phase postselection, which helps us to accurately bound the amount of information an eavesdropper may obtain. We further apply our analysis in sending-or-not-sending twin-field quantum key distribution (SNS-TFQKD) and mode-pairing quantum key distribution (MP-QKD). The simulation results confirm that our precise phase error analysis can noticeably improve the key rate performance especially over long distances in practice. Note that our method does not require alterations to the existing experimental hardware or protocol steps. It can be readily applied within current SNS-TF-QKD and MP-QKD for higher key rate generation.

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arXiv2023

Practical Phase-Coding Side-Channel-Secure Quantum Key Distribution

All kinds of device loopholes give rise to a great obstacle to practical secure quantum key distribution (QKD). In this article, inspired by the original side-channel-secure protocol [Physical Review Applied 12, 054034 (2019)], a new QKD protocol called phase-coding side-channel-secure (PC-SCS) protocol is proposed. This protocol can be immune to all uncorrelated side channels of the source part and all loopholes of the measurement side. A finite-key security analysis against coherent attack of the new protocol is given. The proposed protocol only requires modulation of two phases, which can avoid the challenge of preparing perfect vacuum states. Numerical simulation shows that a practical transmission distance of 300 km can be realized by the PC-SCS protocol.

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