检索结果-南通市图书馆

Near-field wideband beam training for ELAA with uniform circular array

在线全文

学校读者我要写书评

暂无评论

Science China(information Sciences) 2024年第6期67卷 370-383页

作者： Yuhao CHEN Linglong DAI Department of Electronic Engineering Tsinghua UniversityBeijing National Research Center for Information Science and Technology (BNRist)

Extremely large-scale antenna array(ELAA) at millimeter wave(mmWave) and Terahertz(THz)band has been considered a key technology for combating high attenuation in high-frequency bands in future6G communications. Uniform circular arrays(UCAs) have attracted much attention because of their ability to provide flat beamforming gain at all angles. To realize efficient beamforming, beam training is widely used to acquire channel state information. However, with a large antenna number, the beam training overhead in ELAA systems becomes overwhelming. Moreover, with a large bandwidth, the beam defocus effect severely degrades beam training accuracy. To address these issues, this paper proposes a frequency-dependent focusing(FDF)-based beam training scheme to realize effective beam training in near-field wideband ELAA systems with UCA. Specifically, we first analyze the FDF property of UCA, where signals at different subcarriers can simultaneously focus on different distances. Then, by exploiting the FDF property to search different distances using different subcarriers simultaneously, we design a hierarchical codebook and propose an FDFbased beam training scheme. To reveal the effectiveness of the proposed scheme, we compare its necessary beam training overhead with that of existing schemes. Finally, the simulation results demonstrate that the proposed scheme can achieve accurate beam training in near-field wideband UCA systems with a low beam training overhead.

关键词： extremely large-scale antenna array (ELAA) uniform circular array (UCA) near-field wideband beam training

Quantized anomalous Hall resistivity achieved in molecular beam epitaxy-grown Mn Bi2Te4 thin films

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

National Science Review 2024年第2期11卷 24-32页

作者： Yunhe Bai Yuanzhao Li Jianli Luan Ruixuan Liu Wenyu Song Yang Chen Peng-Fei Ji Qinghua Zhang Fanqi Meng Bingbing Tong Lin Li Yuying Jiang Zongwei Gao Lin Gu Jinsong Zhang Yayu Wang Qi-Kun Xue Ke He Yang Feng Xiao Feng State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Institute of Physics Chinese Academy of Sciences School of Materials Science and Engineering Tsinghua University Beijing Academy of Quantum information Sciences Frontier Science center for Quantum information Hefei National Laboratory Southern University of Science and Technology

The intrinsic magnetic topological insulator MnBi2Te4provides a feasible pathway to the high-temperature quantum anomalous Hall（QAH） effect as well as various novel topological quantum phases. Although quantized transport properties have been observed in exfoliated MnBi2Te4thin flakes, it remains a big challenge to achieve molecular beam epitaxy（MBE）-grown MnBi2Te4thin films even close to the quantized regime. In this work, we report the realization of quantized anomalous Hall resistivity in MBE-grown MnBi2Te4thin films with the chemical potential tuned by both controlled in situ oxygen exposure and top gating. We find that elongated post-annealing obviously elevates the temperature to achieve quantization of the Hall resistivity, but also increases the residual longitudinal resistivity, indicating a picture of high-quality QAH puddles weakly coupled by tunnel barriers. These results help to clarify the puzzles in previous experimental studies on MnBi2Te4and to find a way out of the big difficulty in obtaining MnBi2Te4samples showing quantized transport properties.

关键词： intrinsic magnetic topological insulator quantized anomalous Hall resistivity molecular beam epitaxy quantized transport property

Quantum self-attention neural networks for text classification

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science China(information Sciences) 2024年第4期67卷 301-313页

作者： Guangxi LI Xuanqiang ZHAO Xin WANG Institute for Quantum Computing Baidu Research Centre for Quantum Software and information University of Technology Sydney QICI Quantum information and Computation Initiative Department of Computer ScienceThe University of Hong Kong Thrust of Artificial Intelligence Information HubHong Kong University of Science and Technology(Guangzhou)

An emerging direction of quantum computing is to establish meaningful quantum applications in various fields of artificial intelligence, including natural language processing(NLP). Although some efforts based on syntactic analysis have opened the door to research in quantum NLP(QNLP), limitations such as heavy syntactic preprocessing and syntax-dependent network architecture make them impracticable on larger and real-world data sets. In this paper, we propose a new simple network architecture, called the quantum selfattention neural network(QSANN), which can compensate for these limitations. Specifically, we introduce the self-attention mechanism into quantum neural networks and then utilize a Gaussian projected quantum self-attention serving as a sensible quantum version of self-attention. As a result, QSANN is effective and scalable on larger data sets and has the desirable property of being implementable on near-term quantum devices. In particular, our QSANN outperforms the best existing QNLP model based on syntactic analysis as well as a simple classical self-attention neural network in numerical experiments of text classification tasks on public data sets. We further show that our method exhibits robustness to low-level quantum noises and showcases resilience to quantum neural network architectures.

关键词： quantum neural networks self-attention natural language processing text classification parameterized quantum circuits

Experimental demonstration of a quantum downstream access network in continuous variable quantum key distribution with a local local oscillator

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Photonics Research 2024年第6期12卷 1262-1273页

作者： DENGKE QI XIANGYU WANG ZHENGHUA LI JIAYU MA ZIYANG CHEN YUEMING LU SONG YU State Key Laboratory of information Photonics and Optical Communications Beijing University of Posts and TelecommunicationsBeijing 100876China Key Laboratory of Trustworthy Distributed Computing and Service(MoE) Beijing University of Posts and TelecommunicationsBeijing 100876China State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronicsand Center for Quantum Information TechnologyPeking UniversityBeijing 100871China

Quantum networks provide opportunities and challenges across a range of intellectual and technical frontiers,including quantum computation,communication,and *** traditional communication networks,quantum networks utilize quantum bits rather than classical bits to store and transmit *** key distribution(QKD)relying on the principles of quantum mechanics is a key component in quantum networks and enables two parties to produce a shared random secret key,thereby ensuring the security of data *** this work,we propose a cost-effective quantum downstream access network structure in which each user can get their corresponding key information through terminal *** on this structure,we demonstrate the first four-end-users quantum downstream access network in continuous variable QKD with a local local *** contrast to point-to-point continuous variable QKD,the network architecture reevaluates the security of each user and accounts for it accordingly,and each user has a lower tolerance for excess noise as the overall network expands with more ***,the feasibility of the experiment is based on the analysis of the theoretical model,noise analysis,and multiple techniques such as the particle filter and adaptive equalization algorithm used to suppress excess *** results show that each user can get a low level of excess noise and can achieve secret key rates of 546 kbps,535 kbps,522.5 kbps,and 512.5 kbps under a transmission distance of 10 km,respectively,with the finite-size block of 1×10~*** not only verifies the good performance but also provides the foundation for the future multi-user quantum downstream access networks.

关键词： quantum oscillator local

Image encryption algorithm based on multiple chaotic systems and improved Joseph block scrambling

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2024年第10期33卷 248-257页

作者： Dingkang Mou Yumin Dong College of Computer and information Science Chongqing Normal UniversityChongqing 400047China

With the rapid development of digital information technology,images are increasingly used in various *** ensure the security of image data,prevent unauthorized tampering and leakage,maintain personal privacy,and protect intellectual property rights,this study proposes an innovative color image encryption ***,the Mersenne Twister algorithm is utilized to generate high-quality pseudo-random numbers,establishing a robust basis for subsequent ***,two distinct chaotic systems,the autonomous non-Hamiltonian chaotic system and the tentlogistic-cosine chaotic mapping,are employed to produce chaotic random *** chaotic sequences are used to control the encoding and decoding process of the DNA,effectively scrambling the image ***,the complexity of the encryption process is enhanced through improved Joseph block *** experimental verification,research,and analysis,the average value of the information entropy test data reaches as high as ***,the average value of the number of pixels change rate(NPCR)test data is 99.6101%,which closely approaches the ideal value of 99.6094%.This algorithm not only guarantees image quality but also substantially raises the difficulty of decryption.

关键词： mersenne twister algorithm DNA coding confusion pixel XOR operation improved Joseph block scrambling

Simulation extractable SNARKs based on target linearly collision-resistant oracle

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2024年第9期67卷 2853-2866页

作者： WANG LiGuan LI Yuan ZHANG ShuangJun CAI DongLiang KAN HaiBin Shanghai Key Laboratory of Intelligent information Processing School of Computer ScienceFudan UniversityShanghai 200433China Shanghai Engineering Research center of Blockchain Shanghai 200433China Yiwu Research Institute of Fudan University Yiwu 322000China

The famous zero-knowledge succinct non-interactive arguments of knowledge(zk-SNARK) was proposed by Groth in ***, the construction is based on quadratic arithmetic programs which are highly efficient concerning the proof length and the verification complexity. Since then, there has been much progress in designing zk-SNARKs, achieving stronger security,and simulated extractability, which is analogous to non-malleability and has broad applications. In this study, following Groth's pairing-based zk-SNARK, a simulation extractability zk-SNARK under the random oracle model is constructed. Our construction relies on a newly proposed property named target linearly collision-resistant, which is satisfied by random oracles under discrete logarithm assumptions. Compared to the original Groth16 zk-SNARK, in our construction, both parties are allowed to use such a random oracle, aiming to get the same random number. The resulting proof consists of 3 group elements and only 1 pairing equation needs to be verified. Compared to other related works, our construction is shorter in proof length and simpler in verification while preserving simulation extractability. The results also extend to achieve subversion zero-knowledge SNARKs.

关键词： quadratic arithmetic program simulation extractability subversion zero-knowledge succinct non-interactive arguments of knowledge target linearly collision-resistant

Effect of Vacancy Defects on the Properties of CoS_(2) and FeS_(2)

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2024年第3期39卷 627-638页

作者：冯中营 ZHANG Jianmin WANG Xiaowei YANG Wenjin JING Yinlan YANG Yan Department of Science Taiyuan Institute of TechnologyTaiyuan 030008China Computational Physics Research center Taiyuan In-stitute of TechnologyTaiyuan 030008China College of Physics and information Technology Shaanxi Normal UniversityXi’an 710119China Collaborative Innovation center of Extreme Optics Shanxi UniversityTaiyuan 030006China Department of Physics College of ScienceNorth University of ChinaTaiyuan 030051China

In order to explore the effect of vacancy defects on the structural,electronic,magnetic and optical properties of CoS_(2) and FeS_(2),first-principles calculation method was used to investigate the *** calculated results of materials without vacancy are consistent with those reported in the literatures,while the results of materials with vacancy defect were different from those of literatures due to the difference vacancy *** Co vacancy defect hardly changes the half-metallic characteristic of CoS_(2).The Fe vacancy defect changes FeS_(2) from semiconductor to half-metal,and the bottom of the spin-down conduction band changes from the p orbital state of S to the d(t_(2g))orbital state of Fe,while the top of the valence band remains the d orbital d(eg)state of *** half-metallic Co vacancy defects of CoS_(2) and Fe vacancy defects of FeS_(2) are expected to be used in spintronic devices.S vacancy defects make both CoS_(2) and FeS_(2) *** the Co and S vacancy defects lead to the decrease of the magnetic moment of CoS_(2),while both the Fe and S vacancy defects lead to the obvious magnetic property of FeS_(2).Vacancy defects enhance the absorption coefficient of infrared band and long band of visible light obviously,and produce obvious red shift phenomenon,which is expected to be used in photoelectric devices.

关键词： cobalt disulfide iron disulfide vacancy defect fist principles

Physical Layer Encryption of OFDM-PON Based on Quantum Noise Stream Cipher with Polar Code

在线全文

学校读者我要写书评

暂无评论

China Communications 2024年第3期21卷 174-188页

作者： Xu Yinbo Gao Mingyi Zhu Huaqing Chen Bowen Xiang Lian Shen Gangxiang Jiangsu Engineering Research center of Novel Optical Fiber Technology and Communication Network Suzhou Key Laboratory of Advanced Optical Communication Network Technologythe School of Electronic and Information EngineeringSoochow UniversityNo.1 Shizi StreetSuzhou 215006China

Orthogonal frequency division multiplexing passive optical network(OFDM-PON) has superior anti-dispersion property to operate in the C-band of fiber for increased optical power budget. However,the downlink broadcast exposes the physical layer vulnerable to the threat of illegal eavesdropping. Quantum noise stream cipher(QNSC) is a classic physical layer encryption method and well compatible with the OFDM-PON. Meanwhile, it is indispensable to exploit forward error correction(FEC) to control errors in data transmission. However, when QNSC and FEC are jointly coded, the redundant information becomes heavier and thus the code rate of the transmitted signal will be largely reduced. In this work, we propose a physical layer encryption scheme based on polar-code-assisted QNSC. In order to improve the code rate and security of the transmitted signal, we exploit chaotic sequences to yield the redundant bits and utilize the redundant information of the polar code to generate the higher-order encrypted signal in the QNSC scheme with the operation of the *** experimentally demonstrate the encrypted 16/64-QAM, 16/256-QAM, 16/1024-QAM, 16/4096-QAM QNSC signals transmitted over 30-km standard single mode fiber. For the transmitted 16/4096-QAM QNSC signal, compared with the conventional QNSC method, the proposed method increases the code rate from 0.1 to 0.32 with enhanced security.

关键词： physical layer encryption polar code quantum noise stream cipher

Capillary property of Entangled Porous Metallic Wire materials and Its Application in Fluid Buffers:Theoretical Analysis and Experimental Study

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第1期31卷 400-416页

作者： Yu Tang Yiwan Wu Hu Cheng Rong Liu Engineering Research center for Metal Rubber School of Mechanical Engineering and AutomationFuzhou UniversityFuzhou 350156China AECC Guizhou Liyang Aviation Power Co. LTDGuiyang 550014China College of Computer and information Sciences Fujian Agriculture and Forestry UniversityFuzhou 350156China

Strong impact does serious harm to the military industries so it is necessary to choose reasonable cushioning material and design effective buffers to prevent the impact of *** on the capillary property entangled porous metallic wire materials(EPMWM),this paper designed a composite buffer which uses EPMWM and viscous fluid as cushioning materials under the low-speed impact of the recoil force device of weapon equipment(such as artillery,mortar,etc.).Combined with the capillary model,porosity,hydraulic diameter,maximum pore diameter and pore distribution were used to characterize the pore structure characteristics of *** calculation model of the damping force of the composite buffer was *** low-speed impact test of the composite buffer was *** parameters of the buffer under low-speed impact were identified according to the model,and the nonlinear model of damping force was *** test results show that the composite buffer with EPMWM and viscous fluid can absorb the impact energy from the recoil movement effectively,and provide a new method for the buffer design of weapon equipment(such as artillery,mortar,etc.).

关键词： Entangled porous metallic wire materials Capillary property Viscousfluid Low-speed impact Damping force