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IEEE International Symposium on Information Theory

作者： Yi Zhao Bing Qi Xiongfeng Ma Hoi-kwong Lo Li Qian Center for Quantum Information and Quantum Control Department of Physics and Department of Electrical & Computer Engineering University of Toronto Toronto ONT Canada

ISBN: (纸本)142440505X

Decoy state quantum key distribution (QKD) has been proposed as a novel approach to improve dramatically both the security and the performance of practical QKD set-ups. Recently, many theoretical efforts have been made on this topic and have theoretically predicted the high performance of decoy method. However, the gap between theory and experiment remains open. In this paper, we report the first experiments on decoy state QKD, thus bridging the gap. Two protocols of decoy state QKD are implemented: one-decoy protocol over 15 km of standard telecom fiber, and weak+vacuum protocol over 60 km of standard telecom fiber. We implemented the decoy state method on a modified commercial QKD system. The modification we made is simply adding commercial acousto-optic modulator (AOM) on the QKD system. The AOM is used to modulate the intensity of each signal individually, thus implementing the decoy state method. As an important part of implementation, numerical simulation of our set-up is also performed. The simulation shows that standard security proofs give a zero key generation rate at the distance we perform decoy state QKD (both 15 km and 60 km). Therefore decoy state QKD is necessary for long distance secure communication. Our implementation shows explicitly the power and feasibility of decoy method, and brings it to our real-life

关键词： Security Quantum computing Protocols Fiber lasers Laser theory Hydrogen Pulse measurements Physics Telecommunication standards Optical fiber theory

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Smooth patchy control Lyapunov functions

Smooth patchy control Lyapunov functions

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IEEE Conference on Decision and control

作者： Rafal Goebel Christophe Prieur Andrew R. Teel Department of Mathematics University of Washington Seattle WA USA LAAS CNRS Toulouse France Center for Control Dynamical Systems & Computation (CCDC) Department of Electrical and Computer Engineering University of California Santa Barbara CA USA

ISBN: (纸本)1424401704;9781424401703

A smooth patchy control Lyapunov function for a nonlinear 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 decrease condition when the domains overlap. We prove that such a control Lyapunov function exists for any asymptotically controllable nonlinear system. We also show a construction, based on such a Lyapunov function, of a stabilizing hybrid feedback that is robust to measurement noise

关键词： Lyapunov method Nonlinear control systems control systems Noise robustness Noise measurement Nonlinear systems Additive noise State feedback Robust control Robust stability

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Experimental Quantum Key Distribution with Decoy States

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Physical Review Letters 2006年第7期96卷 070502-070502页

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

To increase dramatically the distance and the secure key generation rate of quantum key distribution (QKD), the idea of quantum decoys—signals of different intensities—has recently been proposed. Here, we present the first experimental implementation of decoy state QKD. By making simple modifications to a commercial quantum key distribution system, we show that a secure key generation rate of 165 bit/s, which is 1/4 of the theoretical limit, can be obtained over 15 km of a telecommunication fiber. We also show that with the same experimental parameters, not even a single bit of secure key can be extracted with a non-decoy-state protocol. Compared to building single photon sources, decoy state QKD is a much simpler method for increasing the distance and key generation rate of unconditionally secure QKD.

关键词： Quantum theory

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Learning Distributed Object Pushing: Individual Learning and Distributed Cooperation Protocol

Learning Distributed Object Pushing: Individual Learning and...

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2006 IEEE/RSJ International Conference on Intelligent Robots and Systems

作者： Hossein Aminaiee Majid Nili Ahmadabadi Control and Intelligent Processing Center of Excellence Robotics and AI Lab Department of Electrical and Computer Engineering University of Tehran Iran

In this paper we study learning in cooperative object pushing systems. The proposed approach is based on the idea of learning individual skills and then mapping the required cooperative behaviors on the learned skills. The control point for each individual robot is chosen so as to simplify the design of the reinforcement signal and reduce the role of delayed reward on individual learning in addition to make cooperative protocol simpler. A fuzzy Q-learning system for learning individual object pushing is proposed, together with a method for coordination among the robots to push the object cooperatively. The coordination method takes into account the dynamics of the object and the learned individual skills. The idea of the coordination protocol is based on the notion of ability and active regions defined in this paper. In effect, the cooperation protocol is mapped to a Q-value based policy. Simulation results supportively show that the robots learn individual and cooperative object pushing efficiently

关键词： Protocols Robot kinematics Intelligent robots Fuzzy systems Learning Friction control systems Artificial intelligence Robot control Fuzzy control

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Unconditionally secure key distillation from multiphotons

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Physical Review A 2006年第1期73卷 010302(R)-010302(R)页

作者： Kiyoshi Tamaki 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 Canada M5S 3G4

In this paper, we prove that the unconditionally secure key can be surprisingly extracted from multiphoton emission part in the photon polarization-based quantum key distribution. One example is shown by explicitly proving that one can indeed generate an unconditionally secure key from Alice’s two-photon emission part proposed by Scarani [ et al. Phys. Rev. Lett. 92, 057901 (2004)]. Which is called the Scarani-Acin-Ribordy-Gisin (SARG04) protocol. This protocol uses the same four states as in Bennett-Brassard 1984 (BB84) and differs only in the classical postprocessing protocol. It is, thus, interesting to see how the classical postprocessing of quantum key distribution might qualitatively change its security. We also show that one can generate an unconditionally secure key from the single to the four-photon part in a generalized SARG04 protocol that uses six states. Finally, we also compare the bit error rate threshold of these protocols with the one in the BB84 protocol and the original six-state protocol assuming a depolarizing channel.

关键词： Quantum theory

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Learning Individual Skills and Team Behaviors for Distributed Object Pushing

Learning Individual Skills and Team Behaviors for Distribute...

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IEEE International Conference on Mechatronics and Automation

作者： Hossein Aminaiee Majid Nili Ahmadabadi Control and Intelligent Processing Center of Excellence Robotics Laboratory Department of Electrical and Computer Engineering University of Tehran Tehran Iran

In this paper we discuss a learning approach to distributed object pushing. In the proposed approach, first the required individual skills for single-robot object pushing are learned using a fuzzy reinforcement learning method. Then, the robots learn how to coordinate their actions to push the object to the desired configuration cooperatively in a distributed manner. The proposed team-level learning benefits from the knowledge, which is in the form of a Q-table, that the agent has gained in its individual learning phase by a special design of reward signal and state-action representation. Each robot learns a threshold on its Q-value using a single state reinforcement learning method and pushes the object when the Q-value of its best action in the current state is above this threshold. The reward signal is designed based on the robots' Q-tables and no external critic is needed for learning cooperation. Simulation results show that the robots learn their individual skills and a cooperation protocol to push the object cooperatively

关键词： Robot kinematics Learning Protocols Robot control Robotics and automation Intelligent robots Signal design Mechatronics Process control Intelligent control

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Design and simulation of an adaptive load shedding algorithm using a real network

Design and simulation of an adaptive load shedding algorithm...

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IEEE Power India Conference

作者： H. Seyedi M. Sanaye-Pasand M.R. Dadashzadeh School of Electrical and Computer Engineering University of Tehran Iran Control and Intelligent Processing Center of Excellence University of Tehran Iran Department of Electrical Engineering University of Western Ontario Canada

ISBN: (纸本)0780395255

In this paper a new adaptive under frequency load shedding algorithm is designed. The purpose of this method is to enhance the adaptability of under frequency relays and increase the security of power system during large disturbances. A suitable method to design the proposed adaptive under frequency load shedding scheme is described in detail. After completing the design, it is tested on a real power system by modeling the network in a power system studies software. Simulation results indicate that the proposed method has an improved performance for large disturbances while its response is similar to the conventional scheme for small disturbances

关键词： Algorithm design and analysis Power system simulation Power system relaying Power system security Power system modeling Frequency Design methodology Software testing System testing Software systems

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Anti-windup control for an air-breathing hypersonic vehicle model

Anti-windup control for an air-breathing hypersonic vehicle ...

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AIAA Guidance, Navigation, and control Conference 2006

作者： Groves, Kevin P. Serrani, Andrea Yurkovich, Stephen Bolender, Michael A. Doman, David B. Collaborative Center of Control Science Ohio State University Columbus OH 43210 United States Air Force Research Laboratory Wright-Patterson AFB OH 45433 United States Harris Corporation FL United States Department of Electrical and Computer Engineering 2015 Neil Ave. AIAA United States Department of Electrical and Computer Engineering 2015 Neil Ave. Columbus OH United States AFRL/VACA 2210 Eighth St. United States

ISBN: (纸本)1563478196

An anti-windup controller modification is implemented in control system design for a model of the longitudinal dynamics of an air-breathing hypersonic vehicle. Anti-windup control allows the input constraints to be considered explicitly in the design of linear controllers to track a reference trajectory for the vehicle velocity, altitude, and angle of attack. The presence of anti-windup alleviates the need of keeping large penalties on the magnitude of the control input to avoid the occurrence of saturation. This, in turn, allows tighter tuning of the controller gains to obtain faster and more accurate trajectory tracking. The paper employs recent developments in anti-windup design to deal with the presence of exponentially unstable dynamics, which are typically encountered in air-breathing vehicle models. Simulation results on a fully nonlinear model are presented to validate the controller design. Copyright © 2006 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

关键词： Hypersonic aerodynamics

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Security proof of a three-state quantum-key-distribution protocol without rotational symmetry

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Physical Review A 2006年第4期74卷 042342-042342页

作者： Chi-Hang Fred Fung Hoi-Kwong Lo Center for Quantum Information and Quantum Control Department of Electrical and Computer Engineering University of Toronto Toronto Ont. M5S 3G4 Canada

Standard security proofs of quantum-key-distribution (QKD) protocols often rely on symmetry arguments. In this paper, we prove the security of a three-state protocol that does not possess rotational symmetry. The three-state QKD protocol we consider involves three qubit states, where the first two states ∣0z⟩ and ∣1z⟩ can contribute to key generation, and the third state ∣+⟩=(∣0z⟩+∣1z⟩)∕2 is for channel estimation. This protocol has been proposed and implemented experimentally in some frequency-based QKD systems where the three states can be prepared easily. Thus, by founding on the security of this three-state protocol, we prove that these QKD schemes are, in fact, unconditionally secure against any attacks allowed by quantum mechanics. The main task in our proof is to upper bound the phase error rate of the qubits given the bit error rates observed. Unconditional security can then be proved not only for the ideal case of a single-photon source and perfect detectors, but also for the realistic case of a phase-randomized weak coherent light source and imperfect threshold detectors. Our result in the phase error rate upper bound is independent of the loss in the channel. Also, we compare the three-state protocol with the Bennett-Brassard 1984 (BB84) protocol. For the single-photon source case, our result proves that the BB84 protocol strictly tolerates a higher quantum bit error rate than the three-state protocol, while for the coherent-source case, the BB84 protocol achieves a higher key generation rate and secure distance than the three-state protocol when a decoy-state method is used.

关键词： Quantum cryptography

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Performance of two quantum-key-distribution protocols

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Physical Review A 2006年第1期73卷 012337-012337页

作者： Chi-Hang Fred Fung Kiyoshi Tamaki Hoi-Kwong Lo Center for Quantum Information and Quantum Control Department of Electrical and Computer Engineering University of Toronto Toronto Ont. M5S 3G4 Canada

We compare the performance of Bennett-Brassard 1984 (BB84) and Scarani-Acin-Ribordy-Gisin 2004 (SARG04) protocols, the latter of which was proposed by V. Scarani et al. [Phys. Rev. Lett. 92, 057901 (2004)]. Specifically, in this paper, we investigate the SARG04 protocol with two-way classical communications and the SARG04 protocol with decoy states. In the first part of the paper, we show that the SARG04 scheme with two-way communications can tolerate a higher bit error rate (19.4% for a one-photon source and 6.56% for a two-photon source) than the SARG04 one with one-way communications (10.95% for a one-photon source and 2.71% for a two-photon source). Also, the upper bounds on the bit error rate for the SARG04 protocol with two-way communications are computed in a closed form by considering an individual attack based on a general measurement. In the second part of the paper, we propose employing the idea of decoy states in the SARG04 scheme to obtain unconditional security even when realistic devices are used. We compare the performance of the SARG04 protocol with decoy states and the BB84 one with decoy states. We find that the optimal mean-photon number for the SARG04 scheme is higher than that of the BB84 one when the bit error rate is small. Also, we observe that the SARG04 protocol does not achieve a longer secure distance and a higher key generation rate than the BB84 one, assuming a typical experimental parameter set.

关键词： Quantum theory

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