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Sub-Mbps key-rate continuous-variable quantum key distribution with local-local-oscillator over 100 km fiber

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arXiv 2022年

作者： Pi, Yaodi Wang, Heng Pan, Yan Shao, Yun Li, Yang Yang, Jie Zhang, Yichen Huang, Wei Xu, Bingjie Science and Technology on Communication Security Laboratory Institute of Southwestern Communication Chengdu610041 China State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China

We experimentally demonstrated a sub-Mbps key rate Gaussian-modulated coherent-state continuous-variable quantum key distribution (CV-QKD) over 100 km transmission distance. To efficiently control the excess noise, the quantum signal and the pilot tone are co-transmitted in fiber channel based on wide-band frequency and polarization multiplexing methods. Furthermore, a high-accuracy data-assisted time domain equalization algorithm is carefully designed to compensate the phase noise and polarization variation in low signal-to-noise ratio. The asymptotic secure key rate (SKR) of the demonstrated CV-QKD is experimentally evaluated to be 10.36 Mbps, 2.59 Mbps, and 0.69 Mbps over transmission distance of 50 km, 75 km, and 100 km, respectively. The experimental demonstrated CV-QKD system significantly improves transmission distance and SKR compared to the state-of-art GMCS CV-QKD experimental results, and shows the potential for long-distance and high-speed secure quantum key distribution. © 2022, CC BY.

关键词： Quantum cryptography

Non-Gaussian postselection and virtual photon subtraction in continuous-variable quantum key distribution

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Physical Review A 2016年第1期93卷 012310-012310页

作者： Zhengyu Li Yichen Zhang Xiangyu Wang Bingjie Xu Xiang Peng Hong Guo State Key Laboratory of Advanced Optical Communication Systems and Networks Center for Computational Science and Engineering and Center for Quantum Information Technology 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 State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing 100876 China

Photon subtraction can enhance the performance of continuous-variable quantum key distribution (CV QKD). However, the enhancement effect will be reduced by the imperfections of practical devices, especially the limited efficiency of a single-photon detector. In this paper, we propose a non-Gaussian postselection method to emulate the photon substraction used in coherent-state CV QKD protocols. The virtual photon subtraction not only can avoid the complexity and imperfections of a practical photon-subtraction operation, which extends the secure transmission distance as the ideal case does, but also can be adjusted flexibly according to the channel parameters to optimize the performance. Furthermore, our preliminary tests on the information reconciliation suggest that in the low signal-to-noise ratio regime, the performance of reconciliating the postselected non-Gaussian data is better than that of the Gaussian data, which implies the feasibility of implementing this method practically.

关键词： Quantum cryptography

Realizing a Downstream-Access Network Using Continuous-Variable Quantum Key Distribution

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Physical Review Applied 2021年第6期16卷 064051-064051页

作者： Yundi Huang Tao Shen Xiangyu Wang Ziyang Chen 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 Science and Technology on Communication Security Laboratory Institute of Southwestern Communication Chengdu 610041 China

Quantum key distribution (QKD), which enables the secure distribution of symmetric keys between two legitimate parties, is highly useful in future network security. An access network that connects multiple end users with one network backbone can be combined with QKD to build security for end users in a scalable and cost-effective way. In this paper, we show that a downstream-access network can be implemented using continuous-variable (CV) QKD. The security analysis is conducted independently with other network nodes, which greatly relax the trustfulness requirement on the network nodes. The security is then obtained against other network parties even when the quantum signals are broadcast throughout the network. The passive beam splitter is sufficient to deterministically distribute the quantum signals, and standard CV QKD systems can be directly fitted in the downstream-access network, which makes it more applicable for practical implementations. Numerous simulation results are provided to demonstrate the performance of the CV QKD downstream-access network, where up to 64 end users are shown to be feasible to access the network. We provide the security-analysis framework for realizing CV QKD in the downstream-access network, which will boost the diversity for constructing practical CV QKD networks.

关键词： Optical quantum information processing Photonics Quantum communication Quantum cryptography Quantum information processing with continuous variables Quantum networks communication networks

Practical security analysis of a continuous-variable quantum random number generator with a noisy local oscillator

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arXiv 2020年

作者： Huang, Weinan Zhang, Yichen Zheng, Ziyong Li, Yang Xu, Bingjie Yu, Song State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China Science and Technology on Security Communication Laboratory Institute of Southwestern Communication Chengdu610041 China

A quantum random-number generator (QRNG) can theoretically generate unpredictable random numbers with perfect devices and is an ideal and secure source of random numbers for cryptography. However, the practical implementations always contain imperfections, which will greatly influence the randomness of the final output and even open loopholes to eavesdroppers. Recently, Thewes et al. experimentally demonstrated a continuous-variable eavesdropping attack, based on heterodyne detection, on a trusted continuous-variable QRNG in Phys. Rev. A 100, 052318 (2019), yet like in many other practical continuous-variable QRNG studies, they always supposed the local oscillator was stable and ignored its fluctuation which might lead to security threats such as wavelength attack. In this work, based on the theory of the conditional min-entropy, imperfections of the practical security of continuous-variable QRNGs are systematically analyzed, especially the local oscillator fluctuation under imbalanced homodyne detection. Experiments of a practical QRNG based on vacuum fluctuation are demonstrated to show the influence of local oscillator fluctuation on the total measurement noise variances and the practical conditional min-entropy with beam splitters of different transmittances. Moreover, a local oscillator monitoring method is proposed for the practical continuous-variable QRNG, which can be used to calibrate the practical conditional min-entropy. Copyright © 2020, The Authors. All rights reserved.

关键词： security systems

Phase-reference intensity attack on continuous-variable quantum key distribution with a real local oscillator

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arXiv 2021年

作者： Shao, Yun Li, Yang Wang, Heng Pan, Yan Pi, Yaodi Zhang, Yichen Huang, Wei Xu, Bingjie Science and Technology on Communication Security Laboratory Institute of Southwestern Communication Chengdu610041 China State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China

In practical continuous-variable quantum key distribution system using local local oscillator (LLO CV-QKD), the phase noise related to coherent detection and phase-reference pulse intensity that can be locally calibrated at the receiver side is considered to be trusted noise to improve the performance. However, if the intensity of the phase-reference pulse is not monitored precisely in real-time, a security loophole will be opened for the eavesdropper to launch attacks. To this end, we propose two practical phase-reference pulse intensity attack strategies, where Eve can reduce the trusted phase noise by manipulating the intensity of the phase-reference pulse, thereby hiding her attack on the signal pulse if the total excess noise remains unchanged. The performance of the LLO CV-QKD system under these attacks has been analyzed. We show that precisely monitoring the intensity of the phase-reference pulse in real-time is an essential countermeasure to prevent the proposed attacks. Moreover, an intensity-monitoring scheme for the phase-reference pulse is proposed to strengthen the security of the practical LLO CV-QKD system and make the trusted phase noise model more robust. © 2021, CC BY.

关键词： Phase noise

Sub-Gbps key rate four-state continuous-variable quantum key distribution within metropolitan area

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arXiv 2021年

作者： Wang, Heng Li, Yang Pi, Yaodi Pan, Yan Shao, Yun Ma, Li Yang, Jie Zhang, Yichen Huang, Wei Xu, Bingjie Science and Technology on Communication Security Laboratory Institute of Southwestern Communication Chengdu610041 China State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China

Continuous-variable quantum key distribution (CVQKD) has potential advantages of high secret key rate, which is very suitable for high-speed metropolitan network application. However, the reported highest secret key rates of the CVQKD systems up to now are limited in a few Mbps. Here, we address the fundamental experimental problems and demonstrate a single-carrier four-state CVQKD with sub-Gbps key rate within metropolitan area. In the demonstrated four-state CVQKD using local local oscillator, an ultra-low level of excess noise is obtained and a high efficient post-processing setup is designed for practically extracting the final secure keys. Thus, the achieved secure key rates are 190.54 Mbps and 137.76 Mbps and 52.48 Mbps using linear channel assuming security analysis method and 233.87 Mbps, 133.6 Mbps and 21.53 Mbps using semidefinite programming security analysis method over transmission distances of 5 km, 10 km and 25 km, respectively. This record-breaking result increases the previous secret key rate record by an order of magnitude, which is sufficient to achieve the one-time pad cryptographic task. Our work shows the road for future high-rate and large-scale CVQKD deployment in secure broadband metropolitan and access networks. © 2021, CC BY.

关键词： Quantum cryptography

Sub-Gbps key rate four-state continuous-variable quantum key distribution within metropolitan area

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Research Square

Research Square 2021年

关键词： Quantum theory

High-speed Gaussian modulated continuous-variable quantum key distribution with a local local oscillator based on pilot-tone-assisted phase compensation

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arXiv 2020年

作者： Wang, Heng Pi, Yaodi Huang, Wei Li, Yang Shao, Yun Yang, Jie Liu, Jinlu Zhang, Chenlin Zhang, Yichen Xu, Bingjie Science and Technology on Communication Security Laboratory Institute of Southwestern Communication Chengdu610041 China State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China

A high-speed Gaussian modulated continuous-variable quantum key distribution (CVQKD) with a local local oscillator (LLO) is experimentally demonstrated based on pilot-tone-assisted phase compensation. In the proposed scheme, the frequency-multiplexing and polarization-multiplexing techniques are used for the separate transmission and heterodyne detection between quantum signal and pilot tone, guaranteeing no crosstalk from strong pilot tone to weak quantum signal and different detection requirements of low-noise for quantum signal and high-saturation limitation for pilot tone. Moreover, compared with the conventional CVQKD based on homodyne detection, the proposed LLO-CVQKD scheme can measure X and P quadrature simultaneously using heterodyne detection without need of extra random basis selection. Besides, the phase noise, which contains the fast-drift phase noise due to the relative phase of two independent lasers and the slow-drift phase noise introduced by quantum channel disturbance, has been compensated experimentally in real time, so that a low level of excess noise with a 25km optical fiber channel is obtained for the achievable secure key rate of 7.04 Mbps in the asymptotic regime and 1.85 Mbps under the finite-size block of 107 Copyright © 2020, The Authors. All rights reserved.

关键词： Heterodyne detection

Practical Continuous-variable Quantum Key Distribution with Feasible Optimization Parameters

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arXiv 2021年

作者： Ma, Li Yang, Jie Zhang, Tao Shao, Yun Liu, Jinlu Luo, Yujie Wang, Heng Huang, Wei Fan, Fan Zhou, Chuang Zhang, Liangliang Zhang, Shuai Zhang, Yichen Li, Yang Xu, Bingjie Science and Technology on Communication Security Laboratory Institute of Southwestern Communication Chengdu610041 China State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China

Continuous-variable quantum key distribution (CV-QKD) offers an approach to achieve a potential high secret key rate (SKR) in metropolitan areas. There are several challenges in developing a practical CV-QKD system from the laboratory to the real world. One of the most significant points is that it is really hard to adapt different practical optical fiber conditions for CV-QKD systems with unified hardware. Thus, how to improve the performance of practical CV-QKD systems in the field without modification of the hardware is very important. Here, a systematic optimization method, combining the modulation variance and error correction matrix optimization, is proposed to improve the performance of a practical CV-QKD system with a restricted capacity of postprocessing. The effect of restricted postprocessing capacity on the SKR is modeled as a nonlinear programming problem with modulation variance as an optimization parameter, and the selection of an optimal error correction matrix is studied under the same scheme. The results show that the SKR of a CV-QKD system can be improved by 24% and 200% compared with previous frequently used optimization methods theoretically with a transmission distance of 50 km. Furthermore, the experimental results verify the feasibility and robustness of the proposed method, where the achieved optimal SKR achieved practically deviates Copyright © 2021, The Authors. All rights reserved.

关键词： Quantum cryptography