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Quantum parameter estimation in a spin-boson dephasing quantum system by periodical projective measurements

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Chinese Physics B 2018年第4期27卷 242-249页

作者：杨乐戴宏毅张明 College of Artificial Intelligence National University of Defense Technology Department of Physics National University of Defense Technology Interdisciplinary center for Quantum Information National University of Defense Technology

In this paper,we explore how to estimate the phase damping parameter γ and the tunneling amplitude parameter ？from a spin-boson dephasing quantum model by periodical projective measurements.The preparation of initial states is accomplished by performing the period measurements in our scheme.The parameter γ can be always estimated when projective measurement bases are chosen as θ = π/2 and φ = 0.Based on the estimated value of γ and the interval information of ？,we can select another measurement bases（θ = π/4 and φ = π/2） to obtain the estimated value of ？.A coherent control is indispensable to estimate ？ if γ is in the interval of ？;whereas the control is not necessary if γ is out of the known interval of ？.We establish the relation between the optimal period time and the parameter γ or ？ in terms of Fisher information.Although the optimal measurement period cannot be selected beforehand,the aforementioned relation can be utilized to adjust the measurement period to approach the optimal one.

关键词： parameter estimation periodical projective measurement spin-boson model dephasing quantum system

Investigation of the effect of quantum measurement on parity-time symmetry

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Science China(Physics,Mechanics & Astronomy) 2022年第6期65卷 36-43页

作者： Wei-Chen Wang Yi Xie Man-Chao Zhang Jie Zhang Chun-Wang Wu Ting Chen Bao-Quan Ou Wei Wu Ping-Xing Chen Department of Physics College of Liberal Arts and SciencesNational University of Defense TechnologyChangsha 410073China Interdisciplinary center for Quantum Information National University of Defense TechnologyChangsha 410073China

Symmetry,including the parity-time(PT)-symmetry,is a striking topic,widely discussed and employed in many fields.It is well-known that quantum measurement can destroy or disturb quantum systems.However,can and how does quantum measurement destroy the symmetry of the measured system?To answer the pertinent question,we establish the correlation between the quan-tum measurement and Floquet PT-symmetry and investigate for the first time how the measurement frequency and measurement strength affect the PT-symmetry of the measured system using the 40Ca+ion.It is already shown that the measurement at high frequencies would break the PT symmetry.Notably,even for an inadequately fast measurement frequency,if the measurement strength is sufficiently strong,the PT symmetry breaking can occur.The current work can enhance our knowledge of quantum measurement and symmetry and may inspire further research on the effect of quantum measurement on symmetry.

关键词： quantum measurement PT-symmetry ion trap

Leap trajectory tracking control based on sliding mode theory for hypersonic gliding vehicle

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Journal of Zhejiang university-Science A(Applied Physics & Engineering) 2022年第3期23卷 188-207页

作者： Kai AN Zhen-yun GUO Wei HUANG Xiao-ping XU Science and Technology on Scramjet Laboratory College of Aerospace Science and EngineeringNational University of Defense TechnologyChangsha 410073China Beijing Interdisciplinary center National University of Defense TechnologyBeijing 100101China

The aim of this study was to develop robust tracking control schemes for the 3D leap trajectory of hypersonic gliding vehicles using sliding mode theory. A predictor-corrector guidance method was applied to the generation of the reference trajectory, and drag acceleration was selected as the profile of reference tracking. A combined super-twisting sliding mode controller(CST-SMC) is proposed to decrease the tracking error and guarantee the tracking performance in the presence of system nonlinearities compared to three other common controllers: the linear sliding mode controller(L-SMC), global fast terminal sliding mode controller(GFT-SMC), and super-twisting sliding mode controller(ST-SMC). By using the developed controller, the system state of a second-order drag acceleration tracking error system can approach the global fast terminal sliding manifold in finite time. By using the Lyapunov approach, sufficient conditions are deduced to ensure that the tracking performance is obtained for a closed-loop system. Furthermore, we show that the controller is robust to initial uncertain parameters and other perturbations, as validated by simulation results with appropriate gains.

关键词： Predictor-corrector guidance Drag tracking Sliding mode control(SMC) Super twisting control

Coprime-frequencied sinusoidal modulation for improving the speed of computational ghost imaging with a spatial light modulator

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Chinese Optics Letters 2016年第11期14卷 62-65页

作者：黎全段振涛林惠祖高少博孙帅刘伟涛 College of Science National University of Defense Technology Interdisciplinary center of Quantum Information National University of Defense Technology

Correlation imaging is attracting more and more at tent ion as a novel imaging technique taking advantage of the high-order coherence of light fields.To reconstruct an image oi the object,many frames of different speckle patterns are required.Therefore,the speed of imaging is strongly limited by the speed of the refreshing rate of the light field.We propose a coprime-frequencied sinusoidal modulation method for speckle pattern creation using a spatial light modulator in a computational ghost imaging system to increase the speed of imaging.The performance of the proposed method is discussed as well.

关键词： Imaging techniques Modulation Speckle

Impact of Distribution Fairness Degree and Entanglement Degree on Cooperation

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Chinese Physics Letters 2018年第3期35卷 5-8页

作者：赵鑫刘博阳易英戴宏毅张明 College of Artificial Intelligence National University of Defense Technology School of Management Xiamen University Department of Physics National University of Defense Technology Interdisciplinary center for Quantum Information National University of Defense Technology

We explore the impact of distributional fairness degree and entanglement degree on the cooperation between different players by investigating a modified prisoner＇s dilemma game. We not only introduce a new concept of distributional fairness degree, but also obtain the cooperation conditions for overcoming dilemma in terms of fairness and entanglement inequalities. It is demonstrated that distributional fairness can be of fundamental importance to promote cooperation with the help of quantum entanglement.

关键词： Impact of Distribution Fairness Degree and Entanglement Degree on Cooperation

Quantum Parameter Estimation: From Experimental Design to Constructive Algorithm

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Communications in Theoretical Physics 2017年第11期67卷 641-646页

作者：杨乐陈希张明戴宏毅 College of Mechatronic Engineering and Automation National university of defense Technology College of Science National university of defense Technology Interdisciplinary center for Quantum Information National university of defense Technology

In this paper we design the following two-step scheme to estimate the model parameter ω0 of the quantum system: first we utilize the Fisher information with respect to an intermediate variable v = cos(ω0 t) to determine an optimal initial state and to seek optimal parameters of the POVM measurement operators; second we explore how to estimate ω0 from v by choosing t when a priori information knowledge of ω0 is available. Our optimal initial state can achieve the maximum quantum Fisher information. The formulation of the optimal time t is obtained and the complete algorithm for parameter estimation is presented. We further explore how the lower bound of the estimation deviation depends on the a priori information of the model.

关键词： Fisher information parameter estimation optimal initial state optimal measurement parameters

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基于簇流的P2P流量精确分类技术（英文）

China Communications 2013年第11期10卷 42-51页

作者：何杰杨岳湘乔勇唐川 College of Computer National University of Defense Technology Information center National University of Defense Technology

P2P traffic has always been a dominant portion of Internet traffic since its emergence in the late 1990s.The method used to accurately classify P2P traffic remains a key problem for Internet Service Producers(ISPs)and network managers.This paper proposes a novel approach to the accurate classification of P2P traffic at a fine-grained level,which depends solely on the number of special flows during small time intervals.These special flows,named Clustering Flows(CFs),are defined as the most frequent and steady flows generated by P2P applications.Hence we are able to classify P2P applications by detecting the appearance of corresponding CFs.Compared to existing approaches,our classifier can realise high classification accuracy by exploiting only several generic properties of flows,instead of extracting sophisticated features from host behaviours or transport layer data.We validate our framework on a large set of P2P traffic traces using a Support Vector Machine(SVM).Experimental results show that our approach correctly classifies P2P applications with an average true positive rate of above 98%and a negligible false positive rate of about 0.01%.

关键词：分类精度 P2P 流量互联网服务聚类网络管理人员假阳性率支持向量机

Detecting P2P bots by mining the regional periodicity

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Journal of Zhejiang university-Science C(Computers and Electronics) 2013年第9期14卷 682-700页

作者： Yong QIAO Yue-xiang YANG Jie HE Chuan TANG Ying-zhi ZENG College of Computer National University of Defense Technology Information center National University of Defense Technology

Peer-to-peer (P2P) botnets outperform the traditional Internet relay chat (IRC) botnets in evading detection and they have become a prevailing type of threat to the Internet nowadays.Current methods for detecting P2P botnets,such as similarity analysis of network behavior and machine-learning based classification,cannot handle the challenges brought about by different network scenarios and botnet variants.We noticed that one important but neglected characteristic of P2P bots is that they periodically send requests to update their peer lists or receive commands from botmasters in the command-and-control (C&C) phase.In this paper,we propose a novel detection model named detection by mining regional periodicity (DMRP),including capturing the event time series,mining the hidden periodicity of host behaviors,and evaluating the mined periodic patterns to identify P2P bot traffic.As our detection model is built based on the basic properties of P2P protocols,it is difficult for P2P bots to avoid being detected as long as P2P protocols are employed in their C&C.For hidden periodicity mining,we introduce the so-called regional periodic pattern mining in a time series and present our algorithms to solve the mining problem.The experimental evaluation on public datasets demonstrates that the algorithms are promising for efficient P2P bot detection in the C&C phase.

关键词： P2P botnet detection Regional periodicity Apriori Autocorrelation function Evaluation function

A modified analytical model of the alkali-metal atomic magnetometer employing longitudinal carrier field

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Chinese Physics B 2021年第5期30卷 302-311页

作者：陈畅张燚汪之国江奇渊罗晖杨开勇 College of Advanced Interdisciplinary Studies National University of Defense TechnologyChangsha 410073China Interdisciplinary center for Quantum Information National University of Defense TechnologyChangsha 410073China

Alkali-metal atomic magnetometers employing longitudinal carrier magnetic field have ultrahigh sensitivity to measure transverse magnetic fields and have been applied in a variety of precise-measurement science and technologies.In practice,the magnetometer response is not rigorously proportional to the measured transverse magnetic fields and the existing fundamental analytical model of this magnetometer is effective only when the amplitudes of the measured fields are very small.In this paper,we present a modified analytical model to characterize the practical performance of the magnetometer more definitely.We find out how the longitudinal magnetization of the alkali metal atoms vary with larger transverse fields.The linear-response capacity of the magnetometer is determined by these factors:the amplitude and frequency of the longitudinal carrier field,longitudinal and transverse spin relaxation time of the alkali spins and rotation frequency of the transverse fields.We give a detailed and rigorous theoretical derivation by using the perturbation-iteration method and simulation experiments are conducted to verify the validity and correctness of the proposed modified model.This model can be helpful for measuring larger fields more accurately and configuring a desirable magnetometer with proper linear range.

关键词： alkali-metal atomic magnetometer longitudinal carrier magnetic field linear-response capacity