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Chinese Physics B 2016年第8期25卷 113-116页

作者：蒋招杰周琦陶智明张晓刚张盛楠祝传文林平卫陈景标 State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science and Center for Quantum Information Technology Peking University Beijing 100871 China School of Photoelectric Information University of Electronic Science and Technology Chengdu 611731 China College of Science Guizhou University of Engineering Science Bijie 551700 China National Institute of Metrology Beijing 100029 China

We demonstrate an 852-nm external cavity diode laser（ECDL） system whose wavelength is mainly determined by an interference filter instead of other wavelength selective elements. The Lorentzian linewidth measured by the heterodyne beating between two identical lasers is 28.3 k Hz. Moreover, we test the application of the ECDL in the Faraday atomic *** saturated absorption spectrum, the transmission spectrum of the Faraday atomic filter at 852 nm is measured by using the ECDL. This interference filter ECDL method can also be extended to other wavelengths and widen the application range of diode laser.

关键词： filters diode lasers Faraday effect

Towards visible soliton microcomb generation

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arXiv 2017年

作者： Lee, Seung Hoon Oh, Dong Yoon Yang, Qi-Fan Shen, Boqiang Wang, Heming Yang, Ki Youl Lai, Yu-Hung Yi, Xu Li, Xinbai Vahala, Kerry T. J. Watson Laboratory of Applied Physics California Institute of Technology PasadenaCA91125 United States State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Peking University Beijing100871 China

Frequency combs have applications that extend from the ultra-violet into the mid-infrared bands. Microcombs, a miniature and often semiconductor-chip-based device, can potentially access most of these applications, but are currently more limited in spectral reach. Here, we demonstrate mode-locked silica microcombs with emission near the edge of the visible spectrum. By using both geometrical and modehybridization dispersion control, devices are engineered for soliton generation while also maintaining optical Q factors as high as 80 million. Electronics-bandwidth-compatible (20 GHz) soliton mode locking is achieved with low pumping powers (parametric oscillation threshold powers as low as 5.4 mW). These are the shortest wavelength soliton microcombs demonstrated to date and could be used in miniature optical clocks. The results should also extend to visible and potentially ultra-violet bands. Copyright © 2017, The Authors. All rights reserved.

关键词： Solitons

Advances in Intelligent Systems and Computing

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Preface

Advances in Intelligent Systems and Computing 2018年 678卷 v-vi页

作者： Thampi, Sabu M. Krishnan, Sri Rodriguez, Juan Manuel Corchado Das, Swagatam Wozniak͕, Michal Al-Jumeil, Dhiy School of CS/IT Indian Institute of Information Technology and Management TrivandrumKerala India Department of Electrical and Computer Engineering Ryerson University TorontoON Canada Department of Computer Science University of Salamanca SalamancaSalamanca Spain Electronics and Communication Sciences Unit Indian Statistical Institute Kolkata West Bengal India Department of Systems and Computer Networks Wroclaw University of Science and Technology Wroclaw Poland Faculty of Engineering and Technology Liverpool John Moores University Liverpool United Kingdom

Atomic clock performance beyond the geodetic limit

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arXiv 2018年

作者： McGrew, W.F. Zhang, X. Fasano, R.J. Schaffer, S.A. Beloy, K. Nicolodi, D. Brown, R.C. Hinkley, N. Milani, G. Schioppo, M. Yoon, T.H. Ludlow, A.D. National Institute of Standards and Technology 325 Broadway BoulderCO80305 United States Department of Physics University of Colorado BoulderCO80309 United States State Key Laboratory of Advanced Optical Communication Systems and Networks Institute of Quantum Electronics School of Electronics Engineering and Computer Science Peking University Beijing100871 China Niels Bohr Institute University of Copenhagen Blegdamsvej 17 Copenhagen2100 Denmark Georgia Tech Research Institute AtlantaGA30332 United States Stable Laser Systems BoulderCO80301 United States Istituto Nazionale di Ricerca Metrologica Strada delle Cacce 91 Torino10135 Italy Politecnico di Torino Corso duca degli Abruzzi 24 Torino10125 Italy TeddingtonTW110LW United Kingdom Department of Physics Korea University 145 Anam-ro Seongbuk-gu Seoul02841 Korea Republic of

The passage of time is tracked by counting oscillations of a frequency reference, such as Earth's revolutions or swings of a pendulum. By referencing atomic transitions, frequency (and thus time) can be measured more precisely than any other physical quantity, with the current generation of optical atomic clocks reporting fractional performance below the 10-17level1-5. However, the theory of relativity prescribes that the passage of time is not absolute, but impacted by an observer's reference frame. Consequently, clock measurements exhibit sensitivity to relative velocity, acceleration and gravity potential. Here we demonstrate optical clock measurements surpassing the present-day ability to account for the gravitational distortion of space-time across the surface of Earth. In two independent ytterbium optical lattice clocks, we demonstrate unprecedented levels in three fundamental benchmarks of clock performance. In units of the clock frequency, we report systematic uncertainty of 1.4 × 10-18, measurement instability of 3.2 × 10-19and reproducibility characterised by ten blinded frequency comparisons, yielding a frequency difference of [-7±(5)stat±(8)sys] × 10-19. While differential sensitivity to gravity could degrade the performance of these optical clocks as terrestrial standards of time, this same sensitivity can be used as an exquisite probe of geopotential5-9. Near the surface of Earth, clock comparisons at the 1 × 10-18 level provide 1 cm resolution along gravity, outperforming state-of-the-art geodetic techniques. These optical clocks can further be used to explore geophysical phenomena10, detect gravitational waves11, test general relativity12 and search for dark matter. Copyright © 2018, The Authors. All rights reserved.

关键词： Earth (planet)

Fast High-resolution Miniature Two-photon Microscopy for Brain Imaging in Freely-behaving Mice at the Single-spine Level

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Fast High-resolution Miniature Two-photon Microscopy for Bra...

中国神经科学学会第十二届全国学术会议

作者： Weijian Zong Runlong Wu Mingli Li Yanhui Hu Yijun Li Jinghang Li Hao Rong Haitao Wu Yangyang Xu Yang Lu Hongbo Jia Ming Fan Zhuan Zhou Yunfeng Zhang Aimin Wang Liangyi Chen Heping Cheng State Key Laboratory of Membrane Biology Institute of Molecular Medicine PekingTsinghua Center for Life Sciences Peking University Department of Cognitive Sciences Institute of Basic Medical Sciences Department of Neurobiology Institute of Basic Medical Sciences Brain Research Instrument Innovation Center Suzhou Institute of Biomedical Engineering and Technology Chinese Academy of Sciences State Key Laboratory of Advanced Optical Communication System and Networks School of Electronics Engineering and Computer Science Peking University

Recent developments in miniaturized microscopes have furthered the quest to visualize brain activities and structural dynamics in animals engaged in self-determined behaviors. However, it remains an unmet challenge to resolve activity at single dendritic spines, the elemental units underlying neuronal computation, in freely-behaving animals. Here, we report the design, testing, and application of a fast, high-resolution, miniaturized two-photon microscope（FIRM-TPM） that accomplishes this goal. With a headpiece weighing 2.15 g and a new type of hollow-core photonic crystal fiber to deliver 920-nm femtosecond laser pulses, the FIRM-TPM is capable of imaging commonly used biosensors at high spatiotemporal resolution（0.64 μm laterally and 3.35 μm axially, 40 Hz at 256 × 256 pixels）. Its micro-electromechanical systems scanner also enables random-access capability and free-line scanning at up to 10,000 Hz. It compares favorably with benchtop two-photon microscopy and miniature wide-field fluorescence microscopy in the structural and functional imaging of Thy1-GFP-or GCa MP6 f-labeled neurons. Further, we demonstrate its unique application and robustness with hour-long recording of neuronal activities down to the level of spines in mice experiencing vigorous body and head movements or engaging in social interaction. Thus, our new generation miniature microscope provides neuroscientists the long-sought tool-of-choice for imaging the brain at the synaptic level in freely-behaving animals.

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Efficient rate-adaptive reconciliation for continuous-variable quantum key distribution

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arXiv 2017年

作者： Wang, Xiangyu Zhang, Yichen Yu, Song Bingjie, X.U. Li, Zhengyu Guo, Hong State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications No. 10 Xitucheng Road Beijing100876 China Science and Technology on Communication Security Laboratory Institute of Southwestern Communication No. 6 Chuangye Road Chengdu610041 China State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Center for Quantum Information Technology Center for Computational Science and Engineering Peking University No. 5 Yiheyuan Road Beijing100871 China

Information reconciliation protocol has a significant effect on the secret key rate and maximal transmission distance of continuous-variable quantum key distribution (CV-QKD) systems. We propose an efficient rate-adaptive reconciliation protocol suitable for practical CV-QKD systems with time-varying quantum channel. This protocol changes the code rate of multi-edge type low density parity check codes, by puncturing (increasing the code rate) and shortening (decreasing the code rate) techniques, to enlarge the correctable signal-to-noise ratios regime, thus improves the overall reconciliation efficiency comparing to the original fixed rate reconciliation protocol. We verify our rate-adaptive reconciliation protocol with three typical code rate, i.e., 0.1, 0.05 and 0.02, the reconciliation efficiency keep around 93.5%, 95.4% and 96.4% for different signal-to-noise ratios, which shows the potential of implementing high-performance CV-QKD systems using single code rate matrix. Copyright © 2017, The Authors. All rights reserved.

关键词： Efficiency

High speed continuous variable source-independent quantum random number generation

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arXiv 2017年

作者： Xu, Bingjie Chen, Ziyang Li, Zhengyu Yang, Jie Su, Qi Huang, Wei Zhang, Yichen Guo, Hong Science and Technology on Security Communication Laboratory Institute of Southwestern Communication Chengdu610041 China State Key Laboratory of Cryptography Beijing100878 China State Key Laboratory of Advanced Optical Communication Systems and Networks School of Electronics Engineering and Computer Science Center for Quantum Information Technology Peking University Beijing100871 China State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications Beijing100876 China

As a fundamental phenomenon in nature, randomness has a wide range of applications in the fields of science and engineering. Among different types of randomnumber generators (RNG), quantumrandomnumber generator (QRNG) is a kind of promising RNG as it can provide provable true randomnumbers based on the inherent randomness of fundamental quantum processes. Nevertheless, the randomness from a QRNG can be diminished (or even destroyed) if the devices (especially the entropy source devices) are not perfect or ill-characterized. To eliminate the practical security loopholes from the source, sourceindependentQRNGs, which allow the source to have arbitrary and unknown dimensions, have been introduced and become one of the most important semi-device-independent QRNGs. Herein a method that enables ultra-fast unpredictable quantum random number generation from quadrature fluctuations of quantum optical field without any assumptions on the input states is proposed. Particularly, to estimate a lower bound on the extractable randomness that is independent from side information held by an eavesdropper, a new security analysis framework is established based on the extremality of Gaussian states, which can be easily extended to design and analyze new semi-device-independent continuous variable QRNG protocols. Moreover, the practical imperfections of the QRNG including the effects of excess noise, finite sampling range, finite resolution and asymmetric conjugate quadratures are taken into account and quantitatively analyzed. Finally, the proposed method is experimentally demonstrated to obtain high secure randomnumber generation rates of 15.07Gbits/s in off-line configuration and can potentially achieve 6 Gbits/s by real-time post-processing. Copyright © 2017, arXiv, All rights reserved.

关键词： Random processes

Taxonomy and issues for antifragile-based multimedia cloud computing

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Journal of Reliable Intelligent Environments 2016年第1期2卷 37-49页

作者： Haider, Syed Fawad Abbas, Laraib Ali, Amjad Iqbal, Muddesar Raza, Imran Hussain, Syed Asad Suh, Doug Young Faculty of Computing and Information Technology University of Gujrat Gujrat Pakistan Department of Computer Science Communication and Networks Research Centre COMSATS Institute of Information Technology Lahore Pakistan Pak-UK Institute of Innovative Technologies for Disaster Management University of Gujrat Gujrat Pakistan Department of Electronics and Radio Engineering College of Electronics and Information Kyung Hee University Yongin446-701 Korea Republic of

Cloud computing has become one of the most dynamic and adoptable computing paradigms. Multimedia Cloud Computing (MCC) is one of today’s hot research topic. MCC is proven to be a most dynamic and efficient platform for managing a large amount of multimedia contents with maximum deployment of computing and processing resources at the service provider instead of users. Resilience and dependability are two key constituents to assure the reliability and availability of any service in the presence of errors and system failures. The heterogeneous environment of MCC has given rise to various challenges related to resource allocation and task management. Antifragility is a key to such environments, to let the disorder drive the strength of these systems. This paper is mainly divided into three parts. The first part discusses in detail the available state-of-the-art related to resource management under MCC. Similarly, the second part presents the comprehensive literature review on the task management in MCC. The third part presents the critical analysis and open research issues in MCC which help the researcher to define their research objectives in the field of MCC. © 2016, Springer International Publishing Switzerland.

关键词： Quality of service

Role Selection Cooperative Systems with Energy Harvesting Relays

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Role Selection Cooperative Systems with Energy Harvesting Re...

作者： Ding, Haiyang Da Costa, Daniel B. Suraweera, Himal A. Ge, Jianhua State Key Laboratory of Integrated Service Networks Xidian University Xi'an710071 China Xi'an Communication Institute Xi'an710106 China Department of Computer Engineering Federal University of Ceará Sobral62010-560 Brazil Department of Electrical and Electronic Engineering University of Peradeniya Peradeniya20400 Sri Lanka

In this paper, a three-node energy-harvesting (EH) cooperative system with ROle SElection (ROSE) mechanism, where the cooperative role of each node is dynamically adjusted based on the surrounding wireless fading environment is considered. We first study a benchmark scenario with the fixed role configuration, from which a tight lower bound for the asymptotic outage behavior is derived. For this case, the achievable diversity is limited to two and the system outage behavior at high signal-to-noise ratio (SNR) is affected by the easing-off factor log c0 together with log(log c0), with c0 denoting the source transmit SNR. After that, a dynamic role selection policy is incorporated and the asymptotic analysis shows that the ROSE mechanism can enhance the system diversity order to three, and the decaying law of outage behavior is no longer affected by the log c0 and log(log c0) factors. In addition, the power-splitting receiver achieves the same asymptotic outage performance as that of the ideal EH receiver. Our results reveal that the line-of-sight component is crucial to improve the performance of the EH-based ROSE cooperative system, and the role decision with imperfect channel information has a detrimental effect on the system's diversity gain. © 2016 IEEE.

关键词： Energy harvesting

Modeling and Analysis of Virtualized Multi-Service Cloud Data Centers with Automatic Server Consolidation and Prescribed Service Level Agreements

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Modeling and Analysis of Virtualized Multi-Service Cloud Dat...

IEEE Conference on ALocal computer networks Workshops (LCN Workshops)

作者： Maggie Mashaly Paul J. Kuehn Information Engineering & Technology Department German University in Cairo Cairo Egypt Institute of Communication Networks and Computer Engineering University of Stuttgart Stuttgart Germany

ISBN: (纸本)9781509023486

Cloud Data Centers (CDC) are developing rapidly and will have a major impact on IT infrastructures in the future for reasons of their low ramp-up costs and service delivery/support capabilities for the users. In this paper CDCs with multi-service application classes are considered which are operated under an automatic server consolidation based on parallel hysteresis methods for server activations/deactivations which have been reported on our previous work. Each class is subjected to an individual SLA, e.g., for the average service delay for non-real-time services or for delay percentiles for services with strict response time constraints, and probabilities for service rejection (loss) or migration. The CDC is modeled by a multi-class server cluster (SC) system, each of them represented by a multi-server queuing system which is controlled by a Finite State machine (FSM) for each class of cloud services. The SC systems are analyzed exactly under Markovian assumptions to receive averages and percentiles of response times and probabilities of loss or migration. The method is novel as it minimizes the energy consumption for servers by an automatic server consolidation strategy while guaranteeing the negotiated SLAs. The method is based on a worst case boundary consideration for the delays of arriving service requests and can be useful to understand the parametric influences and to assess the energy saving gains for multi-tier CDCs.

关键词： Servers Time factors Cloud computing Delays Analytical models Computational modeling Load modeling