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Random Bipartite Entanglement from W and W-Like States

Physical Review Letters 2007年第26期98卷 260501-260501页

作者： Ben Fortescue Hoi-Kwong Lo Center for Quantum Information and Quantum Control Department of Electrical and Computer Engineering and Department of Physics University of Toronto Toronto Ontario M5S 3G4 Canada

We describe a protocol for distilling maximally entangled bipartite states between random pairs of parties from those sharing a tripartite W state |W⟩=(1/3)(|100⟩+|010⟩+|001⟩)ABC, and show that the total distillation rate Et∞ [the total number of Einstein-Podolsky-Rosen (EPR) pairs distilled per W, irrespective of who shares them] may be done at a higher rate than EPR distillation between specified pairs of parties. Specifically, the optimal rate for distillation to specified parties has been previously shown to be 0.92 EPR pairs per W, while our protocol can asymptotically distill 1 EPR pair per W between random pairs of parties, which we conjecture to be optimal. We thus demonstrate a tradeoff between overall distillation rate and final distribution of EPR pairs. We further show that there exist states with fixed lower-bounded Et∞, but arbitrarily small distillable entanglement for specified parties.

关键词： Quantum theory

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Quantum key distribution with dual detectors

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Physical Review A 2007年第5期75卷 052304-052304页

作者： Bing Qi Yi Zhao Xiongfeng Ma Hoi-Kwong Lo Li Qian Center for Quantum Information and Quantum Control (CQIQC) Department of Physics and Department of Electrical and Computer Engineering University of Toronto Toronto M5S 3G4 Canada

To improve the performance of a quantum-key-distribution (QKD) system, high speed, low dark count single photon detectors (or low-noise homodyne detectors) are required. However, in practice, a fast detector is usually noisy. Here, we propose a dual-detector method to improve the performance of a practical QKD system with realistic detectors: the legitimate receiver randomly uses either a fast (but noisy) detector or a quiet (but slow) detector to measure the incoming quantum signals. The measurement results from the quiet detector can be used to bound the eavesdropper’s information, while the measurement results from the fast detector are used to generate a secure key. We apply this idea to various QKD protocols. Simulation results demonstrate significant improvements of the secure key rate in the lower loss regime in both Bennett-Brassard 1984 (BB84) protocol with ideal single photon source and Gaussian-modulated coherent states protocol; while for decoy-state BB84 protocol with weak coherent source, the improvement is moderate. We also discuss various practical issues in implementing the dual-detector scheme.

关键词： Quantum theory

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Hybrid Dynamical Systems: Robust Stability and control

Hybrid Dynamical Systems: Robust Stability and Control

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第二十六届中国控制会议

作者： Goebel Rafal Sanfelice Ricardo G. Teel Andrew R. 3518 NE 42 St. SeattleWA 98105USA Center for Control Dynamical Systemsand ComputationDepartment of Electrical and Computer Engineering University of CaliforniaSanta BarbaraCA 93106-9560USA

Modeling issues for hybrid dynamical systems are discussed and fundamental stability analysis tools are *** tools are useful for the development of hybrid control algorithms.

关键词： Hybrid systems stability control

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A genetic-fuzzy control application to ramp metering and variable speed limit control

A genetic-fuzzy control application to ramp metering and var...

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IEEE International Conference on Systems, Man and Cybernetics

作者： Amir Hosein Ghods Ashkan Rahimi Kian Masoud Tabibi Control and Intelligent Processing Center of Excellence Department of Electrical and Computer Engineering University of Tehran Tehran Iran Department of Civil Engineering University of Amir-Kabir Tehran Iran

This paper proposes a fuzzy control approach for the traffic-responsive ramp metering and variable speed limits control, in order to reduce the peak-hour congestion on freeways. The objective of control is to minimize the total time spent in the traffic network. To ease the calibration process of fuzzy controller and improve the overall performance of ramp metering and variable speed limits, genetic algorithm is applied for tuning the fuzzy sets parameters. In order to evaluate the controller's efficiency and applicability, a comparison is made with traditional ALINEA based controller and the fuzzy ramp metering only case by a case-study. The macroscopic traffic model METANET and its extension for dynamic speed limits are used for optimization procedure and presenting the simulation results. The paper concludes that genetic fuzzy control of ramp metering and speed limits is expected to enhance the performance of the freeway traffic network.

关键词： Traffic control Fuzzy control Communication system traffic control Electric breakdown Fuzzy logic Fuzzy sets Nonlinear control systems Velocity control Safety Fuzzy systems

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Experimental study on the Gaussian-modulated coherent-state quantum key distribution over standard telecommunication fibers

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Physical Review A 2007年第5期76卷 052323-052323页

作者： Bing Qi Lei-Lei Huang Li Qian Hoi-Kwong Lo Center for Quantum Information and Quantum Control (CQIQC) Department of Physics and Department of Electrical and Computer Engineering University of Toronto Toronto Ontario Canada M5S 3G4

In this paper, we present a fully fiber-based one-way quantum-key-distribution (QKD) system implementing the Gaussian-modulated coherent-state (GMCS) protocol. The system employs a double Mach-Zehnder interferometer (MZI) configuration in which the weak quantum signal and the strong local oscillator (LO) go through the same fiber between Alice and Bob, and are separated into two paths inside Bob’s terminal. To suppress the LO leakage into the signal path, which is an important contribution to the excess noise, we implemented a scheme combining polarization and frequency multiplexing, achieving an extinction ratio of 70 dB. To further minimize the system excess noise due to phase drift of the double MZI, we propose that, instead of employing phase feedback control, one simply let Alice remap her data by performing a rotation operation. We further present noise analysis both theoretically and experimentally. Our calculation shows that the combined polarization and frequency multiplexing scheme can achieve better stability in practice than the time-multiplexing scheme, because it allows one to use matched fiber lengths for the signal and the LO paths on both sides of the double MZI, greatly reducing the phase instability caused by unmatched fiber lengths. Our experimental noise analysis quantifies the three main contributions to the excess noise, which will be instructive to future studies of the GMCS QKD systems. Finally, we demonstrate, under the “realistic model” in which Eve cannot control the system within Bob’s terminal, a secure key rate of 0.3bit∕pulse over a 5km fiber link. This key rate is about two orders of magnitude higher than that of a practical Bennett-Brassard 1984 protocol QKD system.

关键词： Quantum cryptography

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RELAXED CHARACTERIZATIONS OF SMOOTH PATCHY control LYAPUNOV FUNCTIONS

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IFAC Proceedings Volumes 2007年第12期40卷 486-491页

作者： Rafal Goebel Christophe Prieur Andrew R. Teel Department of Mathematics University of Washington Seattle WA 98195-4350 LAAS–CNRS 7 Avenue du Colonel Roche 31077 Toulouse Cedex 4 France Center for Control Dynamical Systems & Computation Department of Electrical and Computer Engineering University of California Santa Barbara CA 93106-9560

A smooth patchy control Lyapunov function for a nonlinear control system consists of an ordered family of smooth local control Lyapunov functions, whose open domains form a locally finite cover of the state space of the system, and which satisfy a certain arrangement property. In contrast to (Goebel et al., IEEE CDC, 2006), on each intersection of the domains, we do not impose a decrease condition of the local control Lyapunov functions when the index increases. We show a construction, based on such a patchy control Lyapunov function, of a stabilizing hybrid feedback that is robust to measurement noise. Copyrighte 2007 IFAC

关键词： hybrid systems control Lyapunov function stabilization

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TRACKING control IN THE PRESENCE OF NONLINEAR DYNAMIC FRICTIONAL EFFECTS: ROBOT EXTENSION

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Asian Journal of control 2008年第3期1卷

作者： M. Feemster D.M. Dawson A. Behal W. Dixon Matthew Feemster received the B.S degree in Electrical Engineering from Clemson University Clemson South Carolina in December 1994. Upon graduation he remained at Clemson University and received the M.S. degree in Electrical Engineering in 1997. During this time he also served as a research/teaching assistant. His research work focused on the design and implementation of various nonlinear control algorithms with emphasis on the induction motor and mechanical systems with friction present. He is currently working toward his Ph.D. degree in Electrical Engineering at Clemson University. Darren M. Dawson was born in 1962 in Macon Georgia. He received an Associate Degree in Mathematics from Macon Junior College in 1982 and a B.S. Degree in Electrical Engineering from the Georgia Institute of Technology in 1984. He then worked for Westinghouse as a control engineer from 1985 to 1987. In 1987 he returned to the Georgia Institute of Technology where he received the Ph.D. Degree in Electrical Engineering in March 1990. During this time he also served as a research/teaching assistant. In July 1990 he joined the Electrical and Computer Engineering Department and the Center for Advanced Manufacturing (CAM) at Clemson University where he currently holds the position of Professor. Under the CAM director's supervision he currently leads the Robotics and Manufacturing Automation Laboratory which is jointly operated by the Electrical and Mechanical Engineering departments. His main research interests are in the fields of nonlinear based robust adaptive and learning control with application to electro-mechanical systems including robot manipulators motor drives magnetic bearings flexible cables flexible beams and high-speed transport systems. Aman Behal was born in India in 1973. He received his Masters Degree in Electrical Engineering from Indian Institute of Technology Bombay in 1996. He is currently working towards a Ph.D in Controls and Robotics at Clemson University. His research focuses on the control of no

In this paper, we extend the observer/control strategies previously published in [25] to an n -link, serially connected, direct drive, rigid link, revolute robot operating in the presence of nonlinear friction effects modeled by the Lu-Gre model. In addition, we also present a new adaptive control technique for compensating for the nonlinear parameterizable Stribeck effects. Specifically, an adaptive observer/controller scheme is developed which contains a feedforward approximation of the Stribeck effects. This feedforward approximation is used in a composite controller/observer strategy which forces the average square integral of the position tracking error to an arbitrarily small value. Experimental results are included to illustrate the performance of the proposed controllers.

关键词： Friction compensation nonlinear control

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control of discrete linear repetitive processes with ℋ ∞ and 2 - ∞ performance

Control of discrete linear repetitive processes with ℋ ∞ a...

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2007 American control Conference, ACC

作者： Wu, Ligang Lam, James Paszke, Wojciech Galkowski, Krzysztof Rogers, Eric Space Control and Inertial Technology Research Center Harbin Institute of Technology Harbin 150001 China Department of Mechanical Engineering University of Hong Kong Pokfulam Road Hong Kong Hong Kong Institute of Control and Computation Engineering University of Zielona Góra ul. Podgórna 50 65-246 Zielona Góra Poland School of Electronics and Computer Science University of Southampton Southampton SO17 1BJ United Kingdom

ISBN: (纸本)1424409888

This paper considers the control of discrete linear repetitive processes, which are a distinct class of two-dimensional (2-D) discrete linear systems, i.e. information propagation in two independent directions, which are of both system-theoretic and applications interest. In this paper we report new results on the design of control laws with guaranteed levels of performance. In particular, develop algorithms for the design of an ℋ∞ and 2-∞ dynamic output feedback controller which guarantees that the resulting controlled process is stable and has prescribed disturbance attenuation performance as measured by ℋ∞ and 2-∞ norms. © 2007 IEEE.

关键词： Linear systems

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A Dynamic Decoupling control Approach and Its Applications to Chemical Processes

A Dynamic Decoupling Control Approach and Its Applications t...

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American control Conference (ACC)

作者： Qing Zheng Zhongzhou Chen Zhiqiang Gao Center for Advanced Control Technologies Department of Electrical and Computer Engineering Cleveland State University Cleveland OH USA Department of Chemical Engineering University of Massachusetts Amherst MA USA

In this paper, a unique dynamic decoupling control strategy, based on the active disturbance rejection control framework, is proposed for square multivariable systems. With the proposed method, it is shown that a largely unknown square multivariable system is readily decoupled by actively estimating and rejecting the effects of both the internal plant dynamics and external disturbances. By requiring as little information on plant model as possible, the intention is to make the new method practical. Simulation results obtained on two chemical process problems show good performance in the presence of significant unknown disturbances and unmodeled dynamics.

关键词： Chemical processes MIMO control systems Uncertainty Aerospace control Chemical industry electrical equipment industry Cities and towns USA Councils Mathematical model

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Initial Rotor Position Estimation for Sensorless Brushless DC Drives

Initial Rotor Position Estimation for Sensorless Brushless D...

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International Conference on electrical Machines and Systems 2007(ICEMS2007)(第十届国际电机与系统会议)

作者： P. Champa P. Somsiri P. Wipasuramonton P. Nakmahachalasint Industrial Control and Automation Lab National Electronics and Computer Technology Center Thailand Industrial Control and Automation Lab National Electronics and Computer Technology Center Thailand Department of Electrical Engineering Thammasat University Thailand

This paper presents a method to determine the initial rotor position of a brushless DC machine at standstill without a position sensor. The key principle of the rotor position estimation is based on the simple detection and comparison of phase voltage and current responses relating to the stator inductance varied with the position of the rotor magnet. In the proposed method, only three pulse voltage injections are applied and 30 degree resolution can be achieved. Moreover, no knowledge of machine parameters is required. The effectiveness of the proposed method is validated by experimental results.

关键词： Voltage Rotors Phase detection Position measurement Current measurement Inductance measurement Drives Phase estimation Stators Brushless DC motors

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