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Spectroscopy of low-frequency noise and its temperature dependence in a superconducting qubit

Physical Review B 2012年第17期85卷 174521-174521页

作者： Fei Yan Jonas Bylander Simon Gustavsson Fumiki Yoshihara Khalil Harrabi David G. Cory Terry P. Orlando Yasunobu Nakamura Jaw-Shen Tsai William D. Oliver Department of Nuclear Science and Engineering Massachusetts Institute of Technology (MIT) Cambridge Massachusetts 02139 USA Research Laboratory of Electronics MIT Cambridge Massachusetts 02139 USA Institute of Physical and Chemical Research (RIKEN) Wako Saitama 351-0198 Japan Institute for Quantum Computing and Department of Chemistry University of Waterloo Ontario Canada N2L 3G1 Perimeter Institute for Theoretical Physics Waterloo Ontario Canada N2J 2W9 Department of Electrical Engineering and Computer Science MIT Cambridge Massachusetts 02139 USA Green Innovation Research Laboratories NEC Corporation Tsukuba Ibaraki 305-8501 Japan MIT Lincoln Laboratory 244 Wood Street Lexington Massachusetts 02420 USA

We report a direct measurement of the low-frequency noise spectrum in a superconducting flux qubit. Our method uses the noise sensitivity of a free-induction Ramsey interference experiment, comprising free evolution in the presence of noise for a fixed period of time followed by single-shot qubit-state measurement. Repeating this procedure enables Fourier-transform noise spectroscopy with access to frequencies up to the achievable repetition rate, a regime relevant to dephasing in ensemble-averaged time-domain measurements such as Ramsey interferometry. Rotating the qubit's quantization axis allows us to measure two types of noise: effective flux noise and effective critical-current or charge noise. For both noise sources, we observe that the very same 1/f-type power laws measured at considerably higher frequencies (0.2−20 MHz) are consistent with the noise in the 0.01−100-Hz range measured here. We find no evidence of temperature dependence of the noises over 65−200 mK, and also no evidence of time-domain correlations between the two noises. These methods and results are pertinent to the dephasing of all superconducting qubits.

关键词： QUBITS PHYSICS experiments SUPERCONDUCTORS FOURIER transform infrared spectroscopy TIME-domain analysis CORRELATION (Statistics) TEMPERATURE effect

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CMOS compatible integration of Si/SiO2 multilayer GRIN lens optical mode-size converter to SOI-based waveguide

CMOS compatible integration of Si/SiO2 multilayer GRIN lens ...

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Frontiers in Optics, FiO 2011

作者： Loh, Ter-Hoe Wang, Qian Ng, Keh-Ting Lai, Yi-Cheng Ho, Seng-Tiong Data Storage Institute 5 Engineering Drive 1 Singapore 117608 Singapore Department of Electrical Engineering and Computer Science Northwestern University Evanston IL 60208 United States

Vertical mode size transformation from 300nm-thick Si-waveguide to 6~7μm, coupling to standard single-mode fiber was demonstrated using CMOS-compatible Si/SiO2 multilayer on-chip GRIN lens (length~11.5μm). Multilaye... 详细信息

ISBN: (纸本)9781557529176

关键词： Multilayers

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High-dimensional Gaussian graphical model selection: walk summability and local separation criterion

The Journal of Machine Learning Research

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The Journal of Machine Learning Research 2012年第1期13卷

作者： Animashree Anandkumar Vincent Y. F. Tan Furong Huang Alan S. Willsky Electrical Engineering and Computer Science University of California Irvine Irvine CA Data Mining Department Institute for Infocomm Research Singapore Electrical and Computer Engineering National University of Singapore Stochastic Systems Group Laboratory for Information and Decision Systems Massachusetts Institute of Technology Cambridge MA

We consider the problem of high-dimensional Gaussian graphical model selection. We identify a set of graphs for which an efficient estimation algorithm exists, and this algorithm is based on thresholding of empirical conditional covariances. Under a set of transparent conditions, we establish structural consistency (or sparsistency) for the proposed algorithm, when the number of samples n = Ω(Jmin-2 log p), where p is the number of variables and Jmin is the minimum (absolute) edge potential of the graphical model. The sufficient conditions for sparsistency are based on the notion of walk-summability of the model and the presence of sparse local vertex separators in the underlying graph. We also derive novel non-asymptotic necessary conditions on the number of samples required for sparsistency.

关键词： Gaussian graphical model selection high-dimensional learning local-separation property necessary conditions for model selection walk-summability

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An application of Markov jump process model for activity-based indoor Mobility Prediction in wireless networks

An application of Markov jump process model for activity-bas...

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2011 9th International Conference on Frontiers of Information Technology, FIT 2011

作者： Kolodziej, Joanna Wang, Lizhe Ghani, Nasir Khan, Samee Ullah Min-Allah, Nasro Madani, Sajjad A. Li, Hongxiang Department of Mathematics and Computer Science University of Bielsko-Biala Bielsko-Biala Poland School of Informatics and Computing Indiana University Bloomington IN 47405 United States Department of Electrical and Computer Engineering University of New Mexico Albuquerque NM 87131-0001 United States Department of Electrical and Computer Engineering North Dakota State University Fargo ND 58108-5060 United States Department of Computer Science COMSATS Institute of Information Technology Pakistan Department of Electrical and Computer Engineering University of Louisville Louisville KY 40292 United States

ISBN: (纸本)9780769546254

One of the most important objectives of a wireless network is to facilitate a prediction of users' mobility regardless of their point of attachment to the network. In indoor environments the effective users' motion prediction system and wireless localization technology play an important role in all aspects of people's daily lives. In this paper we propose an activity-based continuous-time Markov model to define and predict the human movement patterns. This model is a simple extension of an Activity based Mobility Prediction algorithm using Markov modeling (AMPuMM) technique. Both models are experimentally evaluated in realistic small university campus scenario. The obtained results show us the high efficiency of the jump methodology in the prediction of the students' activities in the indoor campus environment. © 2011 IEEE.

关键词： Wireless networks

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An ultra-fast hybrid simulation framework for ASIP

An ultra-fast hybrid simulation framework for ASIP

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2011 18th IEEE International Conference on Electronics, Circuits and Systems, ICECS 2011

作者： Qiu, Ji Gao, Xiang Jiang, Yifei Xiao, Xu Key Laboratory of Computer System and Architecture Institute of Computing Technology Graduate University of Chinese Academy of Science Beijing 100190 China Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign Urbana IL United States

ISBN: (纸本)9781457718458

ISS (Instruction Set Simulator) plays an important role in pre-silicon software development for ASIP. However, the speed of traditional simulation is too slow to effectively support full-scale software development. In this paper, we propose a hybrid simulation framework which further improves the previous simulation methods by aggressively utilizing the host machine resources. The utilization is achieved by categorizing instructions of ASIP application into two types, namely custom and basic instructions, via binary instrumentation. Then in a way of hybrid simulation, only custom instructions are simulated on the ISS and basic instructions are executed fast and natively on the host machine. We implement this framework for an industrial ASIP to validate our approach. Experimental results show that when the implemented ISS, namely GS-Sim, is applied to practical multimedia decoders, an average simulation speed up to 1058.5MIPS can be achieved, which is 34.7 times of the state-of-art dynamic binary translation simulator and is the fastest to the best of our knowledge. © 2011 IEEE.

关键词： Software design

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Automatic Web service composition based on Horn clauses and Petri nets

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Expert Systems with Applications 2011年第10期38卷 13024-13031页

作者： Tang, Xianfei Jiang, Changjun Zhou, Mengchu Department of Computer Science and Technology Tongji University Shanghai 201804 China Key Laboratory of Embedded System and Service Computing Ministry of Education Tongji University Shanghai 201804 China Department of Electrical and Computer Engineering New Jersey Institute of Technology Newark NJ 07102 United States

This paper introduces an automatic Web service composition method based on logical inference of Horn clauses and Petri nets. The Web service composition problem is transformed into the logical inference problem of Horn clauses by exploring the dependency relations among services. An algorithm is presented, to determine whether the composite service exists in time that is linear in the size of the knowledge base. It can also return the rule set necessary for the composition. Petri nets are chosen to model the rule set and its structural analysis techniques are used to obtain the composite service. © 2010 Elsevier Ltd. All rights reserved.

关键词： Automatic reasoning Knowledge base Petri nets Service composition Web service

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A domain partition model approach to the online fault recovery of FPGA-based reconfigurable systems

A domain partition model approach to the online fault recove...

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作者： Shang, Lihong Zhou, Mi Hu, Yu Yang, Erfu School of Computer Science and Engineering Beihang University Beijing 100191 China Key Laboratory of Computer System and Architecture Institute of Computing Technology Chinese Academy of Sciences Beijing 100190 China Department of Electronic and Electrical Engineering University of Strathclyde Glasgow Gl 1XW United Kingdom

Field programmable gate arrays (FPGAs) are widely used in reliability-critical systems due to their reconfiguration ability. However, with the shrinking device feature size and increasing die area, nowadays FPGAs can be deeply affected by the errors induced by electromigration and radiation. To improve the reliability of FPGA-based reconfigurable systems, a permanent fault recovery approach using a domain partition model is proposed in this paper. In the proposed approach, the fault-tolerant FPGA recovery from faults is realized by reloading a proper configuration from a pool of multiple alternative configurations with overlaps. The overlaps are presented as a set of vectors in the domain partition model. To enhance the reliability, a technical procedure is also presented in which the set of vectors are heuristically filtered so that the corresponding small overlaps can be merged into big ones. Experimental results are provided to demonstrate the effectiveness of the proposed approach through applying it to several benchmark circuits. Compared with previous approaches, the proposed approach increased MTTF by up to 18.87%. Copyright © 2011 The institute of Electronics, Information and Communication Engineers.

关键词： Fault tolerance

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Online fault detection of induction motors using frequency domain independent components analysis

Online fault detection of induction motors using frequency d...

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IEEE International Symposium on Industrial Electronics (ISIE)

作者： Z. Wang C.S. Chang Department of Computer Science Institute of High Performance Computing Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore

This paper proposes an online fault detection method for induction motors using frequency-domain independent component analysis. Frequency-domain results, which are obtained by applying Fast Fourier Transform (FFT) to measured stator current time-domain waveforms, are analyzed with the aim of extracting frequency signatures of healthy and faulty motors with broken rotor-bar or bearing problem. Independent components analysis (ICA) is applied for such an aim to the FFT results. The obtained independent components as well as the FFT results are then used to obtain the combined fault signatures. The proposed method overcomes problems occurring in many existing FFT-based methods. Results using laboratory-collected data demonstrate the robustness of the proposed method, as well as its immunity against measurement noises and motor parameters.

关键词： Induction motors Frequency domain analysis Stators Feature extraction Time domain analysis Noise

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A feature based frequency domain analysis algorithm for fault detection of induction motors

A feature based frequency domain analysis algorithm for faul...

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IEEE Conference on Industrial Electronics and Applications (ICIEA)

作者： Zhaoxia Wang C. S. Chang Yifan Zhang Department of Computer Science Institute of High Performance Computing Singapore Department of Electrical and Computer Engineering National University of Singapore Singapore

This paper studies the stator currents collected from several inverter-fed laboratory induction motors and proposes a new feature based frequency domain analysis method for performing the detection of induction motor faults, such as the broken rotor-bar or bearing fault. The mathematical formulation is presented to calculate the features, which are called FFT-ICA features in this paper. The obtained FFT-ICA features are normalized by using healthy motor as benchmarks to establish a feature database for fault detection. Compare with conventional frequency-domain analysis method, no prior knowledge of the motor parameters or other measurements are required for calculating features. Only one phase stator current waveforms are enough to provide consistent diagnosis of inverter-fed induction motors at different frequencies. The proposed method also outperforms our previous time domain analysis method.

关键词： Induction motors Time frequency analysis Feature extraction Rotors Fault detection Inverters

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Supervisory evolutionary optimization strategy for adaptive maintenance schedules

Supervisory evolutionary optimization strategy for adaptive ...

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IEEE International Symposium on Industrial Electronics (ISIE)

A supervisory strategy is proposed for improving the performance of an evolutionary-algorithm-based system-maintenance optimizer developed in our previous work for offshore power systems. The system-maintenance optimizer generates a set of initial maintenance plans, and exports them to an intelligent maintenance advisor connected to it for implementation. The proposed supervisory strategy uses a set of intelligent rules for adjusting the crossover and mutation rates of the present evolutionary algorithm. A mechanism is developed for refining and generalizing the supervisory rules according to the user's experience. The proposed supervisory strategy aims to improve the search ability and efficiency of the present evolutionary algorithm. Merits of the proposed supervisory strategy are demonstrated in case studies using our system-maintenance optimizer.

关键词： Maintenance engineering Reliability Genetics Markov processes Optimization Mathematical model Equations

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