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Long-Distance Continuous-Variable Quantum Key Distribution over 202.81 km of Fiber

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Physical Review Letters 2020年第1期125卷 010502-010502页

作者： Yichen Zhang Ziyang Chen Stefano Pirandola Xiangyu Wang Chao Zhou Binjie Chu Yijia Zhao Bingjie Xu Song Yu Hong Guo State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing 100876 China State Key Laboratory of Advanced Optical Communication Systems and Networks Department of Electronics and Center for Quantum Information Technology Peking University Beijing 100871 China Department of Computer Science University of York York YO10 5GH United Kingdom Science and Technology on Security Communication Laboratory Institute of Southwestern Communication Chengdu 610041 China

Quantum key distribution provides secure keys resistant to code-breaking quantum computers. The continuous-variable version of quantum key distribution offers the advantages of higher secret key rates in metropolitan areas, as well as the use of standard telecom components that can operate at room temperature. However, the transmission distance of these systems (compared with discrete-variable systems) are currently limited and considered unsuitable for long-distance distribution. Herein, we report the experimental results of long distance continuous-variable quantum key distribution over 202.81 km of ultralow-loss optical fiber by suitably controlling the excess noise and employing highly efficient reconciliation procedures. This record-breaking implementation of the continuous-variable quantum key distribution doubles the previous distance record and shows the road for long-distance and large-scale secure quantum key distribution using room-temperature standard telecom components.

关键词： Optical quantum information processing Quantum cryptography Quantum information processing with continuous variables Quantum optics

Corrigendum to “The lower bound of the weightwise nonlinearity profile of a class of weightwise perfectly balanced functions” [Discrete Appl. Math. 297 (2021) 60–70]

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Discrete Applied Mathematics 2021年 304卷 323-323页

作者： Sihong Su School of Mathematics and Statistics Henan University Kaifeng 475004 China Science and Technology on Communication Security Laboratory Chengdu 610041 China

Quantum proof and high-speed privacy amplification for quantum key distribution

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Physical Review Applied 2025年第5期23卷 054004-054004页

作者： Bing-Qi Yan Jun-Bin Wu Fan Fan Bing-Jie Xu Xiao-Ling Zhang Min Gu Key Laboratory of Atomic and Subatomic Structure and Quantum Control (Ministry of Education) Guangdong Basic Research Center of Excellence for Structure and Fundamental Interactions of Matter School of Physics South China Normal University Guangzhou 510006 China Guangdong Provincial Key Laboratory of Quantum Engineering and Quantum Materials Guangdong-Hong Kong Joint Laboratory of Quantum Matter South China Normal University Guangzhou 510006 China Quantum Science Center of Guangdong-HongKong-Macao Greater Bay Area (Guangdong) Shenzhen 518000 China School of Information and Communication Engineering University of Electronic Science and Technology of China Chengdu 611731 China National Key Laboratory of Security Communication Institute of Southwestern Communication Chengdu 610041 China

Privacy amplification (PA) is a vital step in the postprocessing stage of quantum key distribution, which can extract a secure key from a source partially leaked to the environment. We propose a PA scheme that uses the square hash (SQH)–modular arithmetic hash (MH) function. In consideration of a potential quantum attacker, we use the trace distance as a metric to measure the closeness between two classical-quantum states. We transform a raw key state to a processed state using this scheme and derive the trace distance between the processed state and the ideal target state. It is proven that the trace distance can be reached as small as desired. Additionally, our approach accelerates the SQH-MH function through the number-theoretic transform, reducing the computational complexity to O(nlog n). On the basis of a CPU, a maximum throughput rate of 1.06 Gbit/s is achieved, and the results show that our algorithm demonstrates good stability of the throughput rate when handling tasks with different compression ratios.

关键词： Number theory

Efficient decoy states for the reference-frame-independent measurement-device-independent quantum key distribution

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arXiv 2020年

作者： Lu, Feng-Yu Yin, Zhen-Qiang Fan-Yuan, Guan-Jie Wang, Rong Liu, Hang Wang, Shuang Chen, Wei He, De-Yong Huang, Wei Xu, Bing-Jie Guo, Guang-Can Han, Zheng-Fu Key Laboratory of Quantum Information CAS Center For Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei230026 China State Key Laboratory of Cryptology P. O. Box 5159 Beijing100878 China Science and Technology on Communication Security Laboratory Institute of Southwestern Communication Chengdu Sichuan610041 China

Reference-frame-independent measurement-device-independent quantum key distribution (RFI-MDI-QKD) is a novel protocol that eliminates all possible attacks on the detector side and necessity of reference-frame alignment in source sides. However, its performance may degrade notably due to statistical fluctuations, since more parameters, e.g. yields and error rates for mismatched-basis events, must be accumulated to monitor the security. In this work, we find that the original decoy states method estimates these yields over pessimistically since it ignores the potential relations between different bases. Through processing parameters of different bases jointly, the performance of RFI-MDI-QKD is greatly improved in terms of secret key rate and achievable distance when statistical fluctuations are considered (The statistical fluctuation analysis is the first step to the final analysis of finite key size effect). Our results pave an avenue towards practical RFI-MDI-QKD. Copyright © 2020, The Authors. All rights reserved.

关键词： Statistical mechanics

Finite-size analysis of continuous variable source-independent quantum random number generation

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arXiv 2020年

作者： Zhang, Junyu Zhang, Yichen Zheng, Ziyong Chen, Ziyang Xu, Bingjie Yu, Song State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Center for Quantum Information Technology Peking University Beijing100871 China Science and Technology on Security Communication Laboratory Institute of Southwestern Communication Chengdu610041 China

We study the impact of finite-size effect on continuous variable source-independent quantum random number generation. The central-limit theorem and maximum likelihood estimation theorem are used to derive the formula which could output the statistical fluctuations and determine upper bound of parameters of practical quantum random number generation. With these results, we can see the check data length and confidence probability has intense relevance to the final randomness, which can be adjusted according to the demand in implementation. Besides, other key parameters, such as sampling range size and sampling resolution, have also been considered in detail. It is found that the distribution of quantified output related with sampling range size has significant effects on the loss of final randomness due to finite-size effect. The overall results indicate that the finite-size effect should be taken into consideration for implementing the continuous variable source-independent quantum random number generation in practical. Copyright © 2020, The Authors. All rights reserved.

关键词： Random number generation

Monitoring an untrusted light source with single-photon detectors in measurement-device-independent quantum key distribution

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Physical Review A 2019年第5期99卷 052302-052302页

作者： Yucheng Qiao Gan Wang Zhengyu Li Bingjie Xu Hong Guo State Key Laboratory of Advanced Optical Communication System and Network School of Electronics Engineering and Computer Science Peking University Beijing 100871 China Science and Technology on Security Communication Laboratory Institute of Southwestern Communication Chengdu 610041 China

Measurement-device-independent quantum key distribution (MDI-QKD) is proposed to close the loopholes of the detection part in QKD systems, while it still requires the light source to be trusted. This assumption is not guaranteed in practice, leading to practical secure issues. In this paper, we propose a light source monitoring scheme with single-photon detectors for MDI-QKD, which can guarantee the security of the system under the untrusted source condition with both common decoy state method and the newly proposed five-intensity decoy state method. Moreover, our monitoring scheme performs almost the same as the ideal MDI protocol even considering the imperfect factors in practical systems. Compared to the previous scheme, our work improves the secure key rate and the transmission distance of practical MDI-QKD systems significantly.

关键词： Quantum communication Quantum cryptography

Twin-field quantum key distribution with passive-decoy state

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arXiv 2020年

作者： Teng, Jun Lu, Feng-Yu Yin, Zhen-Qiang Fan-Yuan, Guan-Jie Wang, Rong Wang, Shuang Chen, Wei Huang, Wei Xu, Bing-Jie Guo, Guang-Can Han, Zheng-Fu CAS Key Laboratory of Quantum Information University of Science and Technology of China Hefei230026 China Synergetic Innovation Center of Quantum Information & Quantum Physics University of Science and Technology of China HefeiAnhui230026 China State Key Laboratory of Cryptography P. O. Box 5159 Beijing100878 China Science and Technology on Communication Security Laboratory Institute of Southwestern Communication ChengduSichuan610041 China

Twin-Field quantum key distribution (TF-QKD) and its variants, e.g. Phase-Matching QKD, Sending-or-not-sending QKD, and No Phase Post-Selection TFQKD promise high key rates at long distance to beat the rate distance limit without a repeater. The security proof of these protocols are based on decoy-state method, which is usually performed by actively modulating a variable optical attenuator together with a random number generator in practical experiments, however, active-decoy schemes like this may lead to side channel and could open a security loophole. To enhance the source security of TF-QKD, in this paper, we propose passive-decoy based TF-QKD, in which we combine TF-QKD with the passive-decoy method. And we present a simulation comparing the key generation rate with that in active-decoy, the result shows our scheme performs as good as active decoy TF-QKD, and our scheme could reach satisfactory secret key rates with just a few photon detectors. This shows our work is meaningful in practice. © 2020, CC-BY.

关键词： Random number generation

Finite-key analysis for twin-field quantum key distribution based on generalized operator dominance condition

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arXiv 2020年

作者： Wang, Rui-Qiang Yin, Zhen-Qiang Lu, Feng-Yu Wang, Rong Wang, Shuang Chen, Wei Huang, Wei Xu, Bing-Jie Guo, Guang-Can Han, Zheng-Fu CAS Key Laboratory of Quantum Information University of Science and Technology of China Hefei230026 China Synergetic Innovation Center of Quantum Information & Quantum Physics University of Science and Technology of China HefeiAnhui230026 China State Key Laboratory of Cryptography P. O. Box 5159 Beijing100878 China Science and Technology on Communication Security Laboratory Institute of Southwestern Communication ChengduSichuan610041 China

Quantum key distribution (QKD) can help two distant peers to share secret key bits, whose security is guaranteed by the law of physics. In practice, the secret key rate of a QKD protocol is always lowered with the increasing of channel distance, which severely limits the applications of QKD. Recently, twin-field (TF) QKD has been proposed and intensively studied, since it can beat the rate-distance limit and greatly increase the achievable distance of QKD. Remarkalebly, K. Maeda et. al. proposed a simple finite-key analysis for TF-QKD based on operator dominance condition. Although they showed that their method is sufficient to beat the rate-distance limit, their operator dominance condition is not general, i.e. it can be only applied in three decoy states scenarios, which implies that its key rate cannot be increased by introducing more decoy states, and also cannot reach the asymptotic bound even in case of preparing infinite decoy states and optical pulses. Here, to bridge this gap, we propose an improved finite-key analysis of TF-QKD through devising new operator dominance condition. We show that by adding the number of decoy states, the secret key rate can be furtherly improved and approach the asymptotic bound. Our theory can be directly used in TF-QKD experiment to obtain higher secret key rate. Our results can be directly used in experiments to obtain higher key rates. Copyright © 2020, The Authors. All rights reserved.

关键词： Quantum cryptography

Long-distance continuous-variable quantum key distribution over 202.81 km fiber

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arXiv 2020年

作者： Zhang, Yichen Chen, Ziyang Pirandola, Stefano Wang, Xiangyu Zhou, Chao Chu, Binjie Zhao, Yijia Xu, Bingjie Yu, Song Guo, Hong State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China State Key Laboratory of Advanced Optical Communication Systems and Networks Department of Electronics Center for Quantum Information Technology Peking University Beijing100871 China Computer Science and York Centre for Quantum Technologies University of York YorkYO10 5GH United Kingdom Science and Technology on Security Communication Laboratory Institute of Southwestern Communication Chengdu610041 China

Quantum key distribution (QKD) [1–3] provides secure keys resistant to code-breaking quantum computers. The continuous-variable version of QKD [1, 4–6] offers the advantages of higher secret key rates in metropolitan areas, as well as the use of standard telecom components that can operate at room temperature [7–10]. However, the transmission distance of these systems (compared with discrete-variable systems) are currently limited and considered unsuitable for long-distance distribution [11]. Herein, we report the experimental results of long distance continuous-variable QKD over 202.81 km of ultralow-loss optical fiber by suitably controlling the excess noise and employing highly-efficient reconciliation procedures. This record-breaking implementation of the continuous-variable QKD doubles the previous distance record and shows the road for long-distance and large-scale secure QKD using room-temperature standard telecom components. Copyright © 2020, The Authors. All rights reserved.

关键词： Quantum cryptography