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arXiv 2019年

作者： Li, Richard Y. Albash, Tameem Lidar, Daniel A. Department of Chemistry University of Southern California Los AngelesCA90089 United States Center for Quantum Information Science and Technology University of Southern California Los AngelesCA90089 United States Department of Electrical and Computer Engineering University of New Mexico AlbuquerqueNM87131 United States Department of Physics and Astronomy University of New Mexico AlbuquerqueNM87131 United States Center for Quantum Information and Control University of New Mexico AlbuquerqueNM87131 United States Department of Physics and Astronomy University of Southern California Los AngelesCA90089 United States Department of Electrical Engineering University of Southern California Los AngelesCA90089 United States

Boltzmann machines, a class of machine learning models, are the basis of several deep learning methods that have been successfully applied to both supervised and unsupervised machine learning tasks. These models assume that some given dataset is generated according to a Boltzmann distribution, and the goal of the training procedure is to learn the set of parameters that most closely match the input data distribution. Training such models is difficult due to the intractability of traditional sampling techniques, and proposals using quantum annealers for sampling hope to mitigate the cost associated with sampling. However, real physical devices will inevitably be coupled to the environment, and the strength of this coupling affects the effective temperature of the distributions from which a quantum annealer samples. To counteract this problem, error correction schemes that can effectively reduce the temperature are needed if there is to be some benefit in using quantum annealing for problems at a larger scale, where we might expect the effective temperature of the device to not be sufficiently low. To this end, we have applied nested quantum annealing correction (NQAC) to do unsupervised learning with a small bars and stripes dataset, and to do supervised learning with a coarse-grained MNIST dataset, which consists of black-And-white images of hand-written integers. For both datasets we demonstrate improved training and a concomitant effective temperature reduction at higher noise levels relative to the unencoded case. We also find better performance overall with longer anneal times and offer an interpretation of the results based on a comparison to simulated quantum annealing and spin vector Monte Carlo. A counterintuitive aspect of our results is that the output distribution generally becomes less Gibbs-like with increasing nesting level and increasing anneal times, which shows that improved training performance can be achieved without equilibration to the target Gi

关键词： Temperature

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Superiorization of preconditioned conjugate gradient algorithms for tomographic image reconstruction

arXiv

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arXiv 2018年

作者： Helou, Elias S. Herman, Gabor T. Lin, Chuan Zibetti, Marcelo V.W. Institute of Mathematical Science and Computation University of São Paulo SP Brazil Department of Computer Science Graduate Center City University of New York NY United States School of Electrical Engineering Southwest Jiaotong University Chengdu China Program in Electrical and Computer Engineering Federal University of Technology PR Brazil

Properties of Superiorized Preconditioned Conjugate Gradient (SupPCG) algorithms in image reconstruction from projections are examined. Least squares (LS) is usually chosen for measuring data-inconsistency in these inverse problems. Preconditioned Conjugate Gradient algorithms are fast methods for finding an LS solution. However, for ill-posed problems, such as image reconstruction, an LS solution may not provide good image quality. This can be taken care of by superiorization. A superiorized algorithm leads to images with the value of a secondary criterion (a merit function such as the total variation) improved as compared to images with similar data-inconsistency obtained by the algorithm without superiorization. Numerical experimentation shows that SupPCG can lead to high-quality reconstructions within a remarkably short time. A theoretical analysis is also provided.15A29, 65F22, 65F10, 94A08 Copyright © 2018, The Authors. All rights reserved.

关键词： Image reconstruction

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Going viral: Stability of consensus-driven adoptive spread

arXiv

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arXiv 2018年

作者： Ruf, Sebastian F. Paarporn, Keith Paré, Philip E. Center for Complex Networks Research Northeastern University Department of Electrical and Computer Engineering University of California Santa Barbara United States Division of Decision and Control Systems KTH

The spread of new products in a networked population is often modeled as an epidemic. However, in the case of "complex" contagion, these models do not capture nuanced, dynamic social reinforcement effects in adoption behavior. In this paper, we investigate a model of complex contagion which allows a coevolutionary interplay between adoption, modeled as an SIS epidemic spreading process, and social reinforcement effects, modeled as consensus opinion dynamics. Asymptotic stability analysis of the all-adopt as well as the none-adopt equilibria of the combined opinion-adoption model is provided through the use of Lyapunov arguments. In doing so, sufficient conditions are provided which determine the stability of the "flop" state, where no one adopts the product and everyone's opinion of the product is least favorable, and the "hit" state, where everyone adopts and their opinions are most favorable. These conditions are shown to extend to the bounded confidence opinion dynamic under a stronger assumption on the model parameters. To conclude, numerical simulations demonstrate behavior of the model which reflect findings from the sociology literature on adoption behavior. Copyright © 2018, The Authors. All rights reserved.

关键词： Asymptotic stability

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Secure quantum key distribution with realistic devices

arXiv

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arXiv 2019年

作者： Xu, Feihu Ma, Xiongfeng Zhang, Qiang Lo, Hoi-Kwong Pan, Jian-Wei Hefei National Laboratory for Physical Sciences at Microscale Department of Modern Physics University of Science and Technology of China Hefei230026 China Shanghai Branch CAS Center for Excellence Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai201315 China Center for Quantum Information Institute for Interdisciplinary Information Sciences Tsinghua University Beijing100084 China Center for Quantum Information and Quantum Control Department of Physics Department of Electrical & Computer Engineering University of Toronto TorontoM5S 3G4 Canada

In principle, quantum key distribution (QKD) offers information-theoretic security based on the laws of physics. In practice, however, the imperfections of realistic devices might introduce deviations from the idealized models used in security analyses. Can quantum code-breakers successfully hack real systems by exploiting the side channels? Can quantum code-makers design innovative counter-measures to foil quantum code-breakers? This article reviews theoretical and experimental progress in the practical security aspects of quantum code-making and quantum code-breaking. After numerous attempts, researchers now thoroughly understand and are able to manage the practical imperfections. Recent advances, such as the measurement-device-independent protocol, have closed the critical side channels in the physical implementations, paving the way for secure QKD with realistic devices. Copyright © 2019, The Authors. All rights reserved.

关键词： Quantum cryptography

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A non-orthogonal variational quantum eigensolver

arXiv

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arXiv 2019年

作者： Huggins, William J. Lee, Joonho Baek, Unpil O'Gorman, Bryan Birgitta Whaley, K. Department of Chemistry University of California BerkeleyCA94720 United States Berkeley Quantum Information and Computation Center University of California BerkeleyCA94720 United States Chemical Sciences Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States Department of Physics University of California BerkeleyCA94720 United States Department of Electrical Engineering and Computer Sciences University of California BerkeleyCA94720 United States Department of Chemistry Columbia University New YorkNY10027 United States

Variational algorithms for strongly correlated chemical and materials systems are one of the most promising applications of near-term quantum computers. We present an extension to the variational quantum eigensolver that approximates the ground state of a system by solving a generalized eigenvalue problem in a subspace spanned by a collection of parametrized quantum states. This allows for the systematic improvement of a logical wavefunction ansatz without a significant increase in circuit complexity. To minimize the circuit complexity of this approach, we propose a strategy for efficiently measuring the Hamiltonian and overlap matrix elements between states parametrized by circuits that commute with the total particle number operator. We also propose a classical Monte Carlo scheme to estimate the uncertainty in the ground state energy caused by a finite number of measurements of the matrix elements. We explain how this Monte Carlo procedure can be extended to adaptively schedule the required measurements, reducing the number of circuit executions necessary for a given accuracy. We apply these ideas to two model strongly correlated systems, a square configuration of H4 and the the π-system of Hexatriene (C6H8). We show that it is possible to accurately capture the ground state of both systems using a linear combination of simpler ansatz circuits for which it is impossible individually. Copyright © 2019, The Authors. All rights reserved.

关键词： Ground state

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Adaptive control for revolute joints robot manipulator with uncertain/unknown dynamic parameters and in presence of disturbance in control input 2017

Adaptive control for revolute joints robot manipulator with ...

引用

3rd International Conference on Mechatronics and Robotics engineering, ICMRE 2017

作者： Sakha, Masoud Seyed Shaker, Hamid Reza Department of Control Engineering Faculty of Electrical and Computer Engineering University of Tabriz Tabriz Iranc Iran Center for Energy Informatics University of Southern Denmark Odense Denmark

ISBN: (纸本)9781450352802

This paper presents an effective adaptive controller for revolute joints robot manipulator where the control input is accompanied with a random disturbance (with unknown PSD). It is clear that, disturbance can compromise the overall performance of the system. To cope with this problem, a control technique is proposed which uses the concept of exponential practical stability. Unlike other counterparts, the proposed method does not need information such as the physical parameters of robot and gravitational acceleration. The results show that the proposed controller achieves an excellent performance clearly seen from the tracking error and its derivatives. © 2017 Association for Computing Machinery.

关键词： controllers

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Asymptotic security of discrete-modulation protocols for continuous-variable quantum key distribution

arXiv

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arXiv 2019年

作者： Kaur, Eneet Guha, Saikat Wilde, Mark M. Hearne Institute for Theoretical Physics Department of Physics and Astronomy Louisiana State University Baton RougeLA70803 United States College of Optical Sciences University of Arizona 1630 E. University Blvd. TucsonAZ85719 United States Department of Electrical and Computer Engineering University of Arizona 1230 E Speedway Blvd. TucsonAZ85719 United States Center for Computation and Technology Louisiana State University Baton RougeLA70803 United States

We consider discrete-modulation protocols for continuous-variable quantum key distribution (CVQKD) that employ a modulation constellation consisting of a finite number of coherent states and that use a homodyne-detection receiver. We establish a security proof for collective attacks in the asymptotic regime, and we provide a formula for an achievable secret-key rate. Previous works established security proofs for Gaussian-modulation CV-QKD protocols or for discrete-modulation protocols with two or three coherent states. The main constituents of our approach include approximating a complex, isotropic Gaussian probability distribution by a finite-size Gauss-Hermite constellation, applying entropic continuity bounds, and leveraging previous security proofs for Gaussianmodulation protocols. As an application of our method, we calculate secret-key rates achievable over a pure-loss bosonic channel. Our results indicate that in the high-loss regime and for suffi- ciently large constellation size, the achievable key rates scale optimally, i.e., proportional to the channel's transmissivity, and they approach the rates achieved by a Gaussian-modulation protocol as the constellation size is increased. Copyright © 2019, The Authors. All rights reserved.

关键词： Modulation

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Optimal operation points for ultrafast, highly coherent Ge hole spin-orbit qubits

arXiv

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arXiv 2019年

作者： Wang, Zhanning Marcellina, Elizabeth Hamilton, A.R. Cullen, James H. Rogge, Sven Salfi, Joe Culcer, Dimitrie School of Physics The University of New South Wales SydneyNSW2052 Australia Australian Research Council Centre of Excellence in the Future Low-Energy Electronics Technologies The University of New South Wales SydneyNSW2052 Australia Center for Quantum Computation and Communication Technology The University of New South Wales SydneyNSW2052 Australia Department of Electrical and Computer Engineering University of British Columbia VancouverBCV6T 1Z4 Canada

Strong spin-orbit interactions make hole quantum dots central to the quest for electrical spin qubit manipulation enabling fast, low-power, scalable quantum computation. Yet it is important to establish to what extent spin-orbit coupling exposes qubits to electrical noise, facilitating decoherence. Here, taking Ge as an example, we show that group IV gate-defined hole spin qubits generically exhibit optimal operation points, defined by the top gate electric field, at which they are both fast and long-lived: the dephasing rate vanishes to first order in electric field noise along all directions in space, the electron dipole spin resonance strength is maximised, while relaxation is drastically reduced at small magnetic fields. The existence of optimal operation points is traced to group IV crystal symmetry and properties of the Rashba spin-orbit interaction unique to spin-3/2 systems. Our results overturn the conventional wisdom that fast operation implies reduced lifetimes, and suggest group IV hole spin qubits as ideal platforms for ultra-fast, highly coherent scalable quantum computing. Copyright © 2019, The Authors. All rights reserved.

关键词： Electric fields

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An indirect numerical method for a time-optimal state-constrained control problem in a steady two-dimensional fluid flow

An indirect numerical method for a time-optimal state-constr...

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Symposium on Autonomous Underwater Vehicle Technology (AUV)

作者： Roman Chertovskih Dmitry Karamzin Nathalie T. Khalil Fernando Lobo Pereira Research Center for Systems and Technologies (SYSTEC) Electrical and Computer Engineering Department Faculdade de Engenharia da Universidade do Porto Porto Portugal Federal Research Center “Computer Science and Control” of the Russian Academy of Sciences Moscow Russia

ISBN: (纸本)9781728102542

This article concerns the problem of computing solutions to optimal control problems with state constraints and whose trajectory is also affected by known flow vector fields. This general mathematical framework is particularly pertinent to the requirements underlying the control of Autonomous Underwater Vehicles in realistic scenarii. The key contribution consists in devising a computational indirect method that becomes effective in the numerical computation of extremals to optimal control problems with state constraints by using multipliers of the Maximum Principle in the form of Gamkrelidze whose measure component is ensured to be continuous. The specific problem of time-optimal control of an Autonomous Underwater Vehicle in a bounded space set, subject to the effect of a flow field and with bounded actuation is used to illustrate the proposed approach. The corresponding numerical results are presented and discussed.

关键词： Optimal control Trajectory Autonomous underwater vehicles Planning Boundary value problems Aerospace electronics computer science

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Experimental Demonstration of High-Rate Measurement-Device-Independent Quantum Key Distribution over Asymmetric Channels

引用

Physical Review Letters 2019年第16期122卷 160501-160501页

作者： Hui Liu Wenyuan Wang Kejin Wei Xiao-Tian Fang Li Li Nai-Le Liu Hao Liang Si-Jie Zhang Weijun Zhang Hao Li Lixing You Zhen Wang Hoi-Kwong Lo Teng-Yun Chen Feihu Xu Jian-Wei Pan Shanghai Branch Hefei National Laboratory for Physical Sciences at Microscale and Department of Modern Physics University of Science and Technology of China Shanghai 201315 China CAS Center for Excellence and Synergetic Innovation Center in Quantum Information and Quantum Physics University of Science and Technology of China Shanghai 201315 People’s Republic of China Centre for Quantum Information and Quantum Control (CQIQC) Department of Electrical & Computer Engineering and Department of Physics University of Toronto Toronto Ontario M5S 3G4 Canada State Key Laboratory of Functional Materials for Informatics Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai 200050 China

Measurement-device-independent quantum key distribution (MDI-QKD) can eliminate all detector side channels and it is practical with current technology. Previous implementations of MDI-QKD all used two symmetric channels with similar losses. However, the secret key rate is severely limited when different channels have different losses. Here we report the results of the first high-rate MDI-QKD experiment over asymmetric channels. By using the recent 7-intensity optimization approach, we demonstrate>10×higher key rate than the previous best-known protocols for MDI-QKD in the situation of large channel asymmetry, and extend the secure transmission distance by more than 20–50 km in standard telecom fiber. The results have moved MDI-QKD towards widespread applications in practical network settings, where the channel losses are asymmetric and user nodes could be dynamically added or deleted.

关键词： Quantum cryptography Quantum networks

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