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arXiv 2023年

作者： Zwolak, Justyna P. Taylor, Jacob M. Andrews, Reed Benson, Jared Bryant, Garnett Buterakos, Donovan Chatterjee, Anasua Sarma, Sankar Das Eriksson, Mark A. Greplová, Eliška Gullans, Michael J. Hader, Fabian Kovach, Tyler J. Mundada, Pranav S. Ramsey, Mick Rasmussen, Torbjoern Severin, Brandon Sigillito, Anthony Undseth, Brennan Weber, Brian National Institute of Standards and Technology GaithersburgMD20899 United States Joint Center for Quantum Information and Computer Science University of Maryland College ParkMD20742 United States Department of Physics University of Maryland College ParkMD20742 United States Joint Quantum Institute National Institute of Standards and Technology University of Maryland GaithersburgMD20899 United States HRL Laboratories LLC 3011 Malibu Canyon Road MalibuCA90265 United States Department of Physics University of Wisconsin-Madison MadisonWI53706 United States Center for Quantum Devices Niels Bohr Institute University of Copenhagen Copenhagen2100 Denmark Condensed Matter Theory Center University of Maryland College ParkMD20742 United States Kavli Institute of Nanoscience Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Central Institute of Engineering Electronics and Analytics ZEA-2 - Electronic Systems Forschungszentrum Jülich GmbH Jülich52425 Germany Q-CTRL Santa MonicaCA90401 United States Intel Components Research Intel Corporation HillsboroOR97124 United States Department of Materials University of Oxford Parks Road OxfordOX1 3PH United Kingdom School of Electrical Engineering and Telecommunications The University of New South Wales SydneyNSW2052 Australia Department of Electrical and Systems Engineering University of Pennsylvania PhiladelphiaPA19104 United States QuTech Delft University of Technology Lorentzweg 1 Delft2628 CJ Netherlands Intelligent Geometries LLC Lake Frederick VA22630 United States

Gate-defined quantum dots are a promising candidate system for realizing scalable, coupled qubit systems and serving as a fundamental building block for quantum computers. However, presentday quantum dot devices suffer from imperfections that must be accounted for, which hinders the characterization, tuning, and operation process. Moreover, with an increasing number of quantum dot qubits, the relevant parameter space grows sufficiently to make heuristic control infeasible. Thus, it is imperative that reliable and scalable autonomous tuning approaches are developed. This meeting report outlines current challenges in automating quantum dot device tuning and operation with a particular focus on datasets, benchmarking, and standardization. We also present insights and ideas put forward by the quantum dot community on how to overcome them. We aim to provide guidance and inspiration to researchers invested in automation efforts. Copyright © 2023, The Authors. All rights reserved.

关键词： Nanocrystals

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Growth optimization and device integration of narrow-bandgap graphene nanoribbons

arXiv

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arXiv 2022年

作者： Barin, Gabriela Borin Sun, Qiang Di Giovannantonio, Marco Du, Cheng-Zhuo Wang, Xiao-Ye Llinas, Juan Pablo Mutlu, Zafer Lin, Yuxuan Wilhelm, Jan Overbeck, Jan Daniels, Colin Lamparski, Michael Sahabudeen, Hafeesudeen Perrin, Mickael L. Urgel, José I. Mishra, Shantanu Kinikar, Amogh Widmer, Roland Stolz, Samuel Bommert, Max Pignedoli, Carlo Feng, Xinliang Calame, Michel Müllen, Klaus Narita, Akimitsu Meunier, Vincent Bokor, Jeffrey Fasel, Roman Ruffieux, Pascal Empa Swiss Federal Laboratories for Materials Science and Technology Dübendorf 8600 Switzerland State Key Laboratory of Elemento-Organic Chemistry College of Chemistry Nankai University Tianjin 300071 China Department of Electrical Engineering and Computer Sciences University of California BerkeleyCA94720 United States Institute of Theoretical Physics University of Regensburg RegensburgD-93053 Germany Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute TroyNY12180 United States Center for Advancing Electronics Dresden Department of Chemistry and Food Chemistry TU Dresden Dresden01062 Germany Max Planck Institute for Polymer Research Mainz55128 Germany Department of Chemistry Johannes Gutenberg-Universität Mainz Mainz55128 Germany Organic and Carbon Nanomaterials Unit Okinawa Institute of Science and Technology Graduate University 1919-1 Tancha Onna-son Okinawa904-0495 Japan Department of Chemistry Biochemistry and Pharmaceutical Sciences University of Bern Bern3012 Switzerland

The electronic, optical and magnetic properties of graphene nanoribbons (GNRs) can be engineered by controlling their edge structure and width with atomic precision through bottom-up fabrication based on molecular precursors. This approach offers a unique platform for all-carbon electronic devices but requires careful optimization of the growth conditions to match structural requirements for successful device integration, with GNR length being the most critical parameter. In this work, we study the growth, characterization, and device integration of 5-atom wide armchair GNRs (5-AGNRs), which are expected to have an optimal band gap as active material in switching devices. 5-AGNRs are obtained via on-surface synthesis under ultrahigh vacuum conditions from Br- and I-substituted precursors. We show that the use of I-substituted precursors and the optimization of the initial precursor coverage quintupled the average 5-AGNR length. This significant length increase allowed us to integrate 5-AGNRs into devices and to realize the first field-effect transistor based on narrow bandgap AGNRs that shows switching behavior at room temperature. Our study highlights that optimized growth protocols can successfully bridge between the sub-nanometer scale, where atomic precision is needed to control the electronic properties, and the scale of tens of nanometers relevant for successful device integration of GNRs. Copyright © 2022, The Authors. All rights reserved.

关键词： X ray photoelectron spectroscopy

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Accurate machine-learning based modeling of apparent viscosity of waxy oils mixed with polymeric wax inhibitors

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Flow Measurement and Instrumentation 2025年

作者： Hongyan Lei Muntadher Abed Hussein Tarak Vora Anupam Yadav Asha Rajiv Aman Shankhyan Sachin Jaidka Mehul Manu Issa Mohammed Kadhim Zainab Jamal Hamoodah Fadhil Faez Mehrdad Mottaghi College of Computer and Electrical Engineering Hunan University of Arts and Science Changde hunan 415000 China Department of sciecnes Al-Manara College for Medical Sciences (Maysan) Iraq Marwadi University Research Center Department of Civil Engineering Faculty of Engineering & Technology Marwadi University Rajkot-360003 Gujarat India Department of Computer engineering and Application GLA University Mathura-281406 India Department of Physics & Electronics School of Sciences JAIN (Deemed to be University) Bangalore Karnataka India Centre for Research Impact & Outcome Chitkara University Institute of Engineering and Technology Chitkara University Rajpura 140401 Punjab India Department of Physics Department of Applied Sciences Chandigarh Engineering College Chandigarh Group of Colleges-Jhanjeri Mohali 140307 Punjab India Department of Allied Science (Physics) Graphic Era Hill University Bhimtal India Graphic Era Deemed to be University Dehradun Uttarakhand-248002 India Department of Medical Laboratories Technology Al-Nisour University College Nisour Seq. Karkh Baghdad Iraq Mazaya University college An Nasiriyah Dhi Qar Iraq Department of Dentistry College of Dentistry The Islamic University Najaf Iraq Department of medical analysis Medical laboratory technique college the Islamic University of Al Diwaniyah Al Diwaniyah Iraq Department of medical analysis Medical laboratory technique college the Islamic University of Babylon Babylon Iraq Faculty of chemistry Kabul University Kabul Afghanistan

While producing and then transporting waxy oils through pipeline network systems, wax precipitation commonly leads to issues such as wax build-up, gel creation, and decreased flow, negatively affecting pipeline efficiency. To address these problems, the petroleum industry frequently uses polymeric flow improvers to enhance the rheological properties, thereby increasing the mobility and flowability of oils. Experimental methods to measure oil viscosity are both expensive and time-consuming; hence, having reliable data driven frameworks are necessary in this regard. This work presents the use of accurate artificial intelligence methods including K-nearest neighbors, convolutional neural network, multi-layer perceptron artificial neural network, decision tree, support vector machine, adaptive boosting, random forest and ensemble learning to create smart methods for calculating the apparent viscosity of waxy crude oils that are doped with polymeric additives by actual databank sourced from prior studies. A databank containing 526 datapoints was used to both prepare and validate these machine learning algorithms. The predicted results were then evaluated against actual lab data using both graphical and statistical methods. The outcomes showed a strong agreement between the determined and real values for the constructed models. These developed models offer a way of accurate estimation capability bypassing the need for costly, labor-intensive, and time-consuming experimental procedures.

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Graphene ribbons with suspended masses as transducers in ultra-small nanoelectromechanical accelerometers

arXiv

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arXiv 2020年

作者： Fan, Xuge Forsberg, Fredrik Smith, Anderson D. Schröder, Stephan Wagner, Stefan Rödjegård, Henrik Fischer, Andreas C. Östling, Mikael Lemme, Max C. Niklaus, Frank Department of Micro and Nanosystems School of Electrical Engineering and Computer Science KTH Royal Institute of Technology StockholmSE-10044 Sweden Scania Technical Centre Södertälje15148 Sweden Department of Integrated Devices and Circuits School of Electrical Engineering and Computer Science KTH Royal Institute of Technology KistaSE-164 40 Sweden Senseair AB Delsbo820 60 Sweden AMO GmbH Otto-Blumenthal-Str. 25 Aachen52074 Germany Silex Microsystems AB Järfälla175 26 Sweden Chair of Electronic Devices Faculty of Electrical Engineering and Information Technology RWTH Aachen University Otto-Blumenthal-Str. 25 Aachen52074 Germany

Nanoelectromechanical system (NEMS) sensors and actuators could be of use in the development of next generation mobile, wearable, and implantable devices. However, these NEMS devices require transducers that are ultra-small, sensitive and can be fabricated at low cost. Here, we show that suspended double-layer graphene ribbons with attached silicon proof masses can be used as combined spring-mass and piezoresistive transducers. The transducers, which are realized using processes that are compatible with large-scale semiconductor manufacturing technologies, can yield NEMS accelerometers that occupy at least two orders of magnitude smaller die area than conventional state-of-the-art silicon accelerometers. With our devices, we also extract the Young's modulus values of double-layer graphene and show that the graphene ribbons have significant built-in stresses. Copyright © 2020, The Authors. All rights reserved.

关键词： Accelerometers

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TAROGE-M: Radio Antenna Array on Antarctic High Mountain for Detecting Near-Horizontal Ultra-High Energy Air Showers

arXiv

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arXiv 2022年

作者： Wang, Shih-Hao Nam, Jiwoo Chen, Pisin Chen, Yaocheng Choi, Taejin Ham, Young-Bae Hsu, Shih-Ying Huang, Jian-Jung Huang, Ming-Huey A. Jee, Geonhwa Jung, Jongil Kim, Jieun Kuo, Chung-Yun Kwon, Hyuck-Jin Lee, Changsup Leung, Chung-Hei Liu, Tsung-Che Shiao, Yu-Shao J. Shin, Bok-Kyun Wang, Min-Zu Wang, Yu-Hsin Anker, Astrid Barwick, Steven W. Besson, Dave Z. Bouma, Sjoerd Cataldo, Maddalena Gaswint, Geoffrey Glaser, Christian Hallmann, Steffen Hanson, Jordan C. Henrichs, Jakob Kleinfelder, Stuart A. Lahmann, Robert Meyers, Zachary S. Nelles, Anna Novikov, Alexander Paul, Manuel P. Pyras, Lilly Persichilli, Christopher Plaisier, Ilse Rice-Smith, Ryan Seikh, Mohammad F.H. Tatar, Joulien Welling, Christoph Zhao, Leshan Department of Physics National Taiwan University Taipei10617 Taiwan Leung Center for Cosmology and Particle Astrophysics National Taiwan University Taipei10617 Taiwan Kavli Institute for Particle Astrophysics and Cosmology SLAC National Accelerator Laboratory Stanford University Stanford CA94305 United States Division of Atmospheric Sciences Korea Polar Research Institute Incheon Korea Republic of Department of Polar Science Korea University of Science and Technology Daejeon Korea Republic of Department of Energy Engineering National United University Miaoli Taiwan Department of Astronomy Space Science and Geology Chungnam National University Daejeon34134 Korea Republic of Department of Physics and Astronomy University of Delaware NewarkDE19716 United States Department of Electrophysics National Yang Ming Chiao Tung University Hsinchu300 Taiwan National Nano Device Laboratories Hsinchu300 Taiwan Ulsan National Institute of Science and Technology Ulsan44919 Korea Republic of Department of Physics and Astronomy University of California IrvineCA92697 United States Department of Physics and Astronomy University of Kansas LawrenceKS66045 United States DESY Zeuthen15738 Germany ECAP Friedrich-Alexander-Universität Erlangen-Nürnberg Erlangen91058 Germany Uppsala University Department of Physics and Astronomy UppsalaSE-752 37 Sweden Whittier College Department of Physics WhittierCA90602 United States Department of Electrical Engineering and Computer Science University of California IrvineCA92697 United States Research Cyberinfrastructure Center University of California IrvineCA92697 United States

The TAROGE-M radio observatory is a self-triggered antenna array on top of the ∼2700 m high Mt. Melbourne in Antarctica, designed to detect impulsive geomagnetic emission from extensive air showers induced by ultra-high energy (UHE) particles beyond 1017eV, including cosmic rays, Earth-skimming tau neutrinos, and particularly, the "ANITA anomalous events" (AAE) from near and below the horizon. The six AAE discovered by the ANITA experiment have signal features similar to tau neutrinos but that hypothesis is in tension either with the interaction length predicted by Standard Model or with the flux limits set by other experiments. Their origin remains uncertain, requiring more experimental inputs for clarification. The detection concept of TAROGE-M takes advantage of a high altitude with synoptic view toward the horizon as an efficient signal collector, and the radio quietness as well as strong and near vertical geomagnetic field in Antarctica, enhancing the relative radio signal strength. This approach has a low energy threshold, high duty cycle, and is easy to extend for quickly enlarging statistics. Here we report experimental results from the first TAROGE-M station deployed in January 2020, corresponding to approximately one month of livetime. The station consists of six receiving antennas operating at 180–450 MHz, and can reconstruct source directions of impulsive events with an angular resolution of ∼ 0.3°, calibrated in situ with a drone-borne pulser system. To demonstrate TAROGE-M’s ability to detect UHE air showers, a search for cosmic ray signals in 25.3-days of data together with the detection simulation were conducted, resulting in seven identified candidates. The detected events have a mean reconstructed energy of 0.95+0−0.3146 EeV and zenith angles ranging from 25° to 82°, with both distributions agreeing with the simulations, indicating an energy threshold at about 0.3 EeV. The estimated cosmic ray flux at that energy is (formula presented), also consis

关键词： Cosmic rays

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Robust Control Performance for Open Quantum Systems

arXiv

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arXiv 2020年

作者： Schirmer, Sophie G. Langbein, Frank C. Weidner, Carrie A. Jonckheere, Edmond The Faculty of Science & Engineering Swansea University SwanseaSA2 8PP United Kingdom The School of Computer Science and Informatics Cardiff University CardiffCF24 4AG United Kingdom The Quantum Engineering Technology Laboratories University of Bristol BristolBS8 1FD United Kingdom The Department of Electrical and Computer Engineering University of Southern California Los AngelesCA90089 United States

Robust performance of control schemes for open quantum systems is investigated under classical uncertainties in the generators of the dynamics and nonclassical uncertainties due to decoherence and initial state preparation errors. A formalism is developed to measure performance based on the transmission of a dynamic perturbation or initial state preparation error to the quantum state error. This makes it possible to apply tools from classical robust control such as structured singular value analysis. A difficulty arising from the singularity of the closed-loop Bloch equations for the quantum state is overcome by introducing the #-inversion lemma, a specialized version of the matrix inversion lemma. Under some conditions, this guarantees continuity of the structured singular value at s = 0. Additional difficulties occur when symmetry gives rise to multiple open-loop poles, which under symmetry-breaking unfold into single eigenvalues. The concepts are applied to systems subject to pure decoherence and a general dissipative system example of two qubits in a leaky cavity under laser driving fields and spontaneous emission. A nonclassical performance index, steady-state entanglement quantified by the concurrence, a nonlinear function of the system state, is introduced. Simulations confirm a conflict between entanglement, its log-sensitivity and stability margin under decoherence. Copyright © 2020, The Authors. All rights reserved.

关键词： Robust control

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Roadmap on Atomic-scale Semiconductor Devices

arXiv

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arXiv 2025年

作者： Schofield, Steven R. Fisher, Andrew J. Ginossar, Eran Lyding, Joseph W. Silver, Richard Fei, Fan Namboodiri, Pradeep Wyrick, Jonathan Masteghin, M.G. Cox, D.C. Murdin, B.N. Clowes, S.K. Keizer, Joris G. Simmons, Michelle Y. Stemp, Holly G. Morello, Andrea Voisin, Benoit Rogge, Sven Wolkow, Robert A. Livadaru, Lucian Pitters, Jason Stock, Taylor J.Z. Curson, Neil J. Butera, Robert E. Pavlova, Tatiana V. Jakob, A.M. Spemann, D. Räcke, P. Schmidt-Kaler, F. Jamieson, D.N. Pratiush, Utkarsh Duscher, Gerd Kalinin, Sergei V. Kazazis, Dimitrios Constantinou, Procopios Aeppli, Gabriel Ekinci, Yasin Owen, James H.G. Fowler, Emma Moheimani, S.O. Reza Randall, John N. Misra, Shashank Ivie, Jeffrey Allemang, Christopher R. Anderson, Evan M. Bussmann, Ezra Campbell, Quinn Gao, Xujiao Lu, Tzu-Ming Schmucker, Scott W. London Centre for Nanotechnology University College London 17-19 Gordon St WC1H 0AH United Kingdom Department of Physics and Astronomy University College London WC1E 6BT United Kingdom School of Mathematics and Physics University of Surrey United Kingdom Department of Electrical and Computer Engineering University of Illinois UrbanaIL61801 United States Atom Scale Device Group National Institute of Standards and Technology GaithersburgMD20899 United States Advanced Technology Institute University of Surrey GU2 7XH United Kingdom School of Physics University of New South Wales Sydney Australia School of Electrical Engineering & Telecommunications UNSW Sydney Australia Silicon Quantum Computing Pty Ltd Sydney Australia Australia University of Alberta Department of Physics EdmontonT6G 2E1 Canada National Research Council of Canada Quantum and Nanotechnologies Research Centre 11421 Saskatchewan Drive NW EdmontonT6G 2M9 Canada Department of Electronic and Electrical Engineering University College London WC1E 7JE United Kingdom Laboratory for Physical Sciences University of Maryland College ParkMD20740 United States Prokhorov General Physics Institute The Russian Academy of Sciences Vavilov str. 38 Moscow119991 Russia School of Physics The University of Melbourne ParkvilleVIC3010 Australia Leipzig04318 Germany Universität Leipzig Felix Bloch Institute for Solid State Physics Applied Quantum Systems Leipzig04103 Germany QUANTUM Institut für Physik Johannes Gutenberg-Universität Mainz Mainz55128 Germany Department of Materials Science and Engineering University of Tennessee KnoxvilleTN37996 United States Paul Scherrer Institute Villigen5232 Switzerland Zürich8093 Switzerland Zyvex Labs 1301 N. Plano Road RichardsonTX75081 United States University of Texas DallasTX United States Sandia National Laboratories 1515 Eubank Blvd. SE AlbuquerqueNM87185 United States

Spin states in semiconductors provide exceptionally stable and noise-resistant environments for qubits, positioning them as optimal candidates for reliable quantum computing technologies. The proposal to use nuclear and electronic spins of donor atoms in silicon, introduced by Kane in 1998, sparked a new research field focused on the precise positioning of individual impurity atoms for quantum devices, utilising scanning tunnelling microscopy and ion implantation. This roadmap article reviews the advancements in the 25 years since Kane’s proposal, the current challenges, and the future directions in atomic-scale semiconductor device fabrication and measurement. It covers the quest to create a silicon-based quantum computer and expands to include diverse material systems and fabrication techniques, highlighting the potential for a broad range of semiconductor quantum technological applications. Key developments include phosphorus in silicon devices such as single-atom transistors, arrayed few-donor devices, one- and two-qubit gates, three-dimensional architectures, and the development of a toolbox for future quantum integrated circuits. The roadmap also explores new impurity species like arsenic and antimony for enhanced scalability and higher-dimensional spin systems, new chemistry for dopant precursors and lithographic resists, and the potential for germanium-based devices. Emerging methods, such as photon-based lithography and electron beam manipulation, are discussed for their disruptive potential. This roadmap charts the path toward scalable quantum computing and advanced semiconductor quantum technologies, emphasising the critical intersections of experiment, technological development, and theory. © 2025, CC BY.

关键词： Qubits

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Artificial intelligence enabled radio propagation for communications - Part I: Channel characterization and antenna-channel optimization

arXiv

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arXiv 2021年

作者： Huang, Chen He, Ruisi Ai, Bo Molisch, Andreas F. Lau, Buon Kiong Haneda, Katsuyuki Liu, Bo Wang, Cheng-Xiang Yang, Mi Oestges, Claude Zhong, Zhangdui The Purple Mountain Laboratories Nanjing211111 China The National Mobile Communications Research Laboratory School of Information Science and Engineering Southeast University Nanjing210096 China The State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing100044 China The Key Laboratory of Railway Industry of Broadband Mobile Information Communications Beijing Jiaotong University Beijing100044 China The School of Information Engineering Zhengzhou University Zhengzhou450001 China Peng Cheng Laboratory Shenzhen518055 China The Ming Hsieh Department of Electrical and Computer Engineering University of Southern California Los AngelesCA90089 United States The Department of Electrical and Information Technology Lund University Lund22100 Sweden The Department of Radio Science and Engineering Aalto University Aalto00076 Finland The School of Engineering University of Glasgow GlasgowG12 8QQ United Kingdom The Purple Mountain Laboratories Nanjing211111 China The Institute of Information and Communication Technologies Electronics and Applied Mathematics Universite Catholique de Louvain Louvain-la-Neuve 1348 Belgium

To provide higher data rates, as well as better coverage, cost efficiency, security, adaptability, and scalability, the 5G and beyond 5G networks are developed with various artificial intelligence techniques. In this two-part paper, we investigate the application of artificial intelligence (AI) and in particular machine learning (ML) to the study of wireless propagation channels. It firstly provides a comprehensive overview of ML for channel characterization and ML-based antenna-channel optimization in this first part, and then it gives a state-of-the-art literature review of channel scenario identification and channel modeling in Part II. Fundamental results and key concepts of ML for communication networks are presented, and widely used ML methods for channel data processing, propagation channel estimation, and characterization are analyzed and compared. A discussion of challenges and future research directions for ML-enabled next generation networks of the topics covered in this part rounds off the paper. © 2021, CC BY-NC-ND.

关键词： Machine learning

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Soft X-ray high-harmonic generation in an anti-resonant hollow core fiber driven by a 3 µm ultrafast laser

arXiv

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arXiv 2025年

作者： Morrill, Drew Hettel, Will Carlson, Daniel Shearer, Benjamin Klein, Clay Thurston, Jeremy Golba, Grzegorz Larsen, Rae Seifert, Gabriella Uhrich, James Lesko, Daniel Nguyen, Tin Nghia Arisholm, Gunnar Knight, Jonathan Diddams, Scott Murnane, Margaret Kapteyn, Henry Hemmer, Michaël JILA & STROBE NSF Science & Technology Center University of Colorado & NIST BoulderCO80309 United States Electrical Computer and Energy Engineering University of Colorado BoulderCO80309 United States Department of Physics University of Colorado BoulderCO80309 United States Postboks 25 KjellerNO-2027 Norway Centre for Photonics and Photonic Materials Department of Physics University of Bath BathBA2 7AY United Kingdom Kapteyn-Murnane Laboratories Inc. 4775 Walnut Street #102 BoulderCO80301 United States

High-harmonic upconversion driven by a mid-infrared femtosecond laser can generate coherent soft X-ray beams in a tabletop-scale setup. Here, we report on a compact ytterbium-pumped optical parametric chirped pulse amplifier (OPCPA) laser system seeded by an all-fiber front-end and employing periodically-poled lithium niobate (PPLN) nonlinear media operated near the pulse fluence limits of current commercially available PPLN crystals. The OPCPA delivers 3 μm wavelength pulses with 775 μJ energy at 1 kHz repetition rate, with transform-limited 120 fs pulse duration, diffraction-limited beam quality, and ultrahigh 0.33% rms energy stability over >18 hours. Using this laser, we generate soft X-ray high harmonics (HHG) in argon gas by focusing into a low-loss, high-pressure gas-filled anti-resonant hollow core fiber (ARHCF), generating coherent light at photon energies up to the argon L-edge (250 eV) and carbon K-edge (284 eV), with high beam quality and ~1% rms energy stability. This work demonstrates soft X-ray HHG in a high-efficiency guided-wave phase matched geometry, overcoming the high losses inherent to mid-IR propagation in unstructured waveguides, or the short interaction lengths of gas cells or jets. The ARHCF can operate long term without damage, and with the repetition rate, stability and robustness required for demanding applications in spectro-microscopy and imaging. Finally, we discuss routes for maximizing the soft X-ray HHG flux by driving He at higher laser intensities using either 1.5 µm or 3 µm—the signal and idler wavelengths of the laser. © 2025, CC BY.

关键词： Ultrashort pulses

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Analog Versus Hybrid Precoding for Multiuser Massive MIMO with Quantized CSI Feedback

arXiv

引用

arXiv 2020年

作者： Xu, Jindan Wang, Kezhi Xu, Wei Zhao, Yaqiong Jin, Shi Alouini, Mohamed-Slim National Mobile Communications Research Laboratory Southeast University Nanjing210096 China National Mobile Communications Research Laboratory Southeast University Nanjing210096 China Purple Mountain Laboratories Nanjing210000 China Department of Computer and Information Sciences Northumbria University Newcastle United Kingdom Computer Electrical and Mathematical Science and Engineering Division King Abdullah University of Science and Technology Thuwal23955 Saudi Arabia

In this letter, we study the performance of a downlink multiuser massive multiple-input multiple-output (MIMO) system with sub-connected structure over limited feedback channels. Tight rate approximations are theoretically analyzed for the system with pure analog precoding and hybrid precoding. The effect of quantized analog and digital precoding is characterized in the derived expressions. Furthermore, it is revealed that the pure analog precoding outperforms the hybrid precoding using maximal-ratio transmission (MRT) or zero forcing (ZF) under certain conditions, and we theoretically characterize the conditions in closed form with respect to signal-to-noise ratio (SNR), the number of users and the number of feedback bits. Numerical results verify the derived conclusions on both Rayleigh channels and mmWave channels. Copyright © 2020, The Authors. All rights reserved.

关键词： MIMO systems

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