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IEEE International Symposium on Information Theory

作者： Kai Chen Hoi-Kwong Lo Center for Quantum Information and Quantum Control Department of Electrical and Computer Engineering Department of Physics University of Toronto Toronto ONT Canada

ISBN: (纸本)0780391500

We propose a wide class of distillation schemes for multi-partite entangled states that are CSS-states. Our proposal provides not only superior efficiency, but also new insights on the connection between CSS-states and bipartite graph states. We then consider the applications of our distillation schemes for two cryptographic tasks - namely, (a) conference key agreement and (b) quantum sharing of classical secrets. In particular, we construct "prepare-and-measure" protocols. Also we study the yield of those protocols and the threshold value of the fidelity above which the protocols can function securely. Surprisingly, our protocols function securely even when the initial state does not violate the standard Bell-inequalities for GHZ states. Experimental realization involving only bipartite entanglement is also suggested

关键词： Quantum entanglement Cryptographic protocols Quantum computing Cryptography Cascading style sheets Bipartite graph Quantum mechanics Physics Proposals Paramagnetic resonance

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NEW RECURSIVE LEAST SQUARE ALGORITHMS WITHOUT USING THE INITIAL INFORMATION

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IFAC Proceedings Volumes 2005年第1期38卷 137-141页

作者： Zhonghua Quan Soohee Han Wook Hyun Kwon School of Electrical Engineering & Computer Science Seoul National University Seoul 151-742 Korea Engineering Research Center for Advanced Control & Instrumentation Seoul National University Seoul 151-742 Korea

In this paper, new types of recursive least square (RLS) algorithms, without using the initial information of a parameter or a state to be estimated, are proposed. The proposed RLS algorithm is first obtained for a generic linear model and is then extended to a state estimator for a stochastic state-space model. Compared with the existing algorithms, the proposed RLS algorithms are simpler and more numerically stable. It is shown, by simulation studies, that the proposed RLS algorithms have better numerical stability for digital computation than existing algorithms.

关键词： Estimation initial information Recursive Least-Squares state estimator numerical stability

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Practical decoy state for quantum key distribution

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Physical Review A 2005年第1期72卷 012326-012326页

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

Decoy states have recently been proposed as a useful method for substantially improving the performance of quantum key distribution (QKD). Here, we present a general theory of the decoy state protocol based on only two decoy states and one signal state. We perform optimization on the choice of intensities of the two decoy states and the signal state. Our result shows that a decoy state protocol with only two types of decoy states—the vacuum and a weak decoy state—asymptotically approaches the theoretical limit of the most general type of decoy state protocol (with an infinite number of decoy states). We also present a one-decoy-state protocol. Moreover, we provide estimations on the effects of statistical fluctuations and suggest that, even for long-distance (larger than 100 km) QKD, our two-decoy-state protocol can be implemented with only a few hours of experimental data. In conclusion, decoy state quantum key distribution is highly practical.

关键词： Quantum theory

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Inefficiency and classical communication bounds for conversion between partially entangled pure bipartite states

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Physical Review A 2005年第3期72卷 032336-032336页

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

We derive lower limits on the inefficiency and classical communication costs of dilution between two-term bipartite pure states that are partially entangled. We first calculate explicit relations between the allowable error and classical communication costs of entanglement dilution using a previously described protocol, then consider a two-stage dilution from singlets with this protocol followed by some unknown protocol for conversion between partially entangled states. Applying overall lower bounds on classical communication and inefficiency to this two-stage protocol, we derive bounds for the unknown protocol. In addition we derive analogous (but looser) bounds for general pure states.

关键词： Quantum cryptography

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Decoy State Quantum Key Distribution

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Physical Review Letters 2005年第23期94卷 230504-230504页

作者： Hoi-Kwong Lo Xiongfeng Ma Kai Chen Center for Quantum Information and Quantum Control Department of Electrical & Computer Engineering and Department of Physics University of Toronto Toronto Ontario M5S 3G4 Canada

There has been much interest in quantum key distribution. Experimentally, quantum key distribution over 150 km of commercial Telecom fibers has been successfully performed. The crucial issue in quantum key distribution is its security. Unfortunately, all recent experiments are, in principle, insecure due to real-life imperfections. Here, we propose a method that can for the first time make most of those experiments secure by using essentially the same hardware. Our method is to use decoy states to detect eavesdropping attacks. As a consequence, we have the best of both worlds—enjoying unconditional security guaranteed by the fundamental laws of physics and yet dramatically surpassing even some of the best experimental performances reported in the literature.

关键词： Quantum theory

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Reconfigurable sliding-mode control design using genetic algorithms and eigenstructure assignment

Reconfigurable sliding-mode control design using genetic alg...

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International Conference on control and Automation (ICCA)

作者： A.E. Ashari M.J. Yazdanpanah A.K. Sedigh Control and Intelligent Processing Center of Excellence Electrical and Computer Engineering Department University of Tehran Tehran Iran Electrical and Electronics Engineering Department K.N. Toosi University of Technology Tehran Iran

This paper proposes a reconfigurable control system design methodology using the sliding-mode control. The advantage of the proposed sliding-mode reconfigurable control methodology is that it is more robust than the simple static reconfigurable feedback. An approach is suggested to redesign the sliding surface for the after-fault variable structure controller using the genetic algorithms. So, the new sliding-mode controller is capable of preserving much of the dynamics of the original unfailed system. Simulation results are provided to show the effectiveness of the proposed method.

关键词： Sliding mode control Algorithm design and analysis Genetic algorithms control systems Feedback Robust control Stability Java Uncertainty State-space methods

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Output feedback reconfigurable controller design using eigenstructure assignment: post fault order change

Output feedback reconfigurable controller design using eigen...

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International Conference on control and Automation (ICCA)

作者： A.E. Ashari A.K. Sedigh M.J. Yazdanpanah Control and Intelligent Processing Center of Excellence Electrical and Computer Engineering Department University of Tehran Tehran Iran Electrical and Electronics Engineering Department K.N. Toosi University of Technology Tehran Iran

This paper proposes a reconfigurable controller design method for multivariable systems, which is capable of dealing with order-change problems that may occur in an after-fault system. A new method is proposed to recover the nominal closed-loop performance after a fault occurrence in the system. This approach uses the eigenstructure assignment. Unlike the previously developed approaches, the new method can be implemented in the case when the fault leads to order change of the after-fault model. Also, it can be used to solve the problems in which the set of after-fault open-loop and closed-loop eigenvalues have common elements, especially when the system becomes uncontrollable or unobservable due to the fault. The method guarantees the stability of the reconfigured closed-loop system in the presence of output feedback. Finally, simulation results are provided to show the effectiveness of the proposed method for an aircraft model.

关键词： Output feedback control systems Stability Eigenvalues and eigenfunctions Sliding mode control Design methodology MIMO Process control Open loop systems Java

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A new protection scheme for fault location and relay by matrix operation method in transmission lines

A new protection scheme for fault location and relay by matr...

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2005 IEEE/PES Transmission and DistributionConference and Exhibition - Asia and Pacific

作者： Zuo, X.F. Kuribayashi, H. Inagaki, T. Tsuji, K. Hiyama, T. IEEE Development Center Marketing and Engineering Division Kyuki Co. Fukuoka 815-0031 Japan Toyama East Synthesis Control Station Hokuriku Electric Power Co. Toyama 930-8543 Japan Techno Tsuji Ltd. Toyama 939-8136 Japan Department of Electrical and Computer Engineering Kumamoto University Kumamoto 860-8555 Japan

ISBN: (纸本)0780391144

This paper presents additional functions of the newly developed matrix operation type protection relay in power transmission lines. The paper presents the basic principle of fault location, the function of integrated protection, corresponding of the system configuration, the regular surveillance, and the results of simulation test. The general equations, which are utilized for the fault detection and the fault location, are derived from the basic equations based on the principle of Kirchhoff s first and second laws for the study transmission system. The proposed protection relay, differing from the conventional digital ones, enable to generalize the required protection functions such as the grounding fault protection, the short-circuit fault protection, the main and the backup protection based on a equivalent circuit for the study system. The function of regular surveillance can be realized to satisfy the voltage balance calculated by the off-line constants and the estimated on-line parameters synthetically. It ensures effectively the reliability of the proposed protection system. The new functions are developed naturally from the principles of the matrix operation type protection relay. Simulation studies and laboratory experiments have clarified the fact that the proposed protection scheme provides an innovative way to solve many problems still remained. © 2005 IEEE.

关键词： Electric power system protection

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Generalized state scaling-based robust control of nonlinear systems and applications to triangular systems

Generalized state scaling-based robust control of nonlinear ...

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American control Conference (ACC)

作者： P. Krishnamurthy F. Khorrami Control/Robotics Research Laboratory(CRRL) Department of Electrical and Computer Engineering Six Metrotech Center Polytechnic University Brooklyn NY USA

In this paper, we propose a high-gain scaling based controller to achieve global state-feedback stabilization of a general class of nonlinear systems which are allowed to contain uncertain functions of all the states and the control input as long as polynomial bounds on ratios of some uncertain system terms are available. The design is based on a high-gain scaling involving appropriate powers of a high-gain scaling parameter which is a dynamic signal driven by the state. The designed controller has a very simple structure being essentially a dynamic extension and a linear feedback with state-dependent dynamic gains. The obtained results are applicable to both lower triangular (strict-feedback) and upper triangular (feedforward) structures and also to systems without any triangular structure as long as a set of inequalities involving powers of the polynomial bounds on the ratios of the uncertain system terms and scaling orders is solvable. The stability analysis is based on our recent results on uniform solvability of coupled state-dependent Lyapunov equations.

关键词： Robust control Nonlinear systems Nonlinear control systems control systems Polynomials Uncertain systems Signal design Nonlinear dynamical systems Linear feedback control systems State feedback

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GODZILA: a low-resource algorithm for path planning in unknown environments

GODZILA: a low-resource algorithm for path planning in unkno...

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American control Conference (ACC)

作者： P. Krishnamurthy F. Khorrami Control/Robotics Research Laboratory(CRRL) Department of Electrical and Computer Engineering Six Metrotech Center Polytechnic University Brooklyn NY USA

In this paper, we propose a novel path-planning and obstacle avoidance algorithm GODZILA for navigation in unknown environments. No prior knowledge of the environment is required. The path-planning algorithm follows a purely local approach using only the current range sensor measurements at each sampling instant and requiring only a small number of stored variables in memory. No map of the environment is built during navigation. This minimizes the memory and computational requirements for implementation of the algorithm, a feature that is especially attractive for small autonomous vehicles. The algorithm utilizes three components: an optimization algorithm, a local straight-line path planner to visible targets, and random navigation. It is proved, for navigation in any finite-dimensional space, that the path-planning algorithm converges in finite time with probability 1. The performance of the algorithm is demonstrated through simulations for path-planning in two-dimensional and three-dimensional spaces. It is seen that a relatively small number of range sensor measurements is sufficient even in complex unknown environments.

关键词： Path planning Navigation Remotely operated vehicles Mobile robots Current measurement Sampling methods Cost function Trajectory Robot sensing systems Orbital robotics

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