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arXiv 2023年

作者： Wang, Zhe Zhang, Jiayi Du, Hongyang Niyato, Dusit Cui, Shuguang Ai, Bo Debbah, Mérouane Letaief, Khaled B. Poor, H. Vincent The School of Electronic and Information Engineering Frontiers Science Center for Smart High-speed Railway System Beijing Jiaotong University Beijing100044 China The School of Computer Science and Engineering Nanyang Technological University Singapore639798 Singapore Shenzhen518172 China The Department of Broadband Communication Peng Cheng Laboratory Shenzhen518000 China The Center for 6G Technology The Khalifa University of Science and Technology Abu Dhabi United Arab Emirates Hong Kong The Department of Electrical and Computer Engineering Princeton University PrincetonNJ08544 United States

Extremely large-scale multiple-input-multiple-output (XL-MIMO), which offers vast spatial degrees of freedom, has emerged as a potentially pivotal enabling technology for the sixth generation (6G) of wireless mobile networks. With its growing significance, both opportunities and challenges are concurrently manifesting. This paper presents a comprehensive survey of research on XL-MIMO wireless systems. In particular, we introduce four XL-MIMO hardware architectures: uniform linear array (ULA)-based XL-MIMO, uniform planar array (UPA)-based XL-MIMO utilizing either patch antennas or point antennas, and continuous aperture (CAP)-based XL-MIMO. We comprehensively analyze and discuss their characteristics and interrelationships. Following this, we introduce several electromagnetic characteristics and general distance boundaries in XL-MIMO. Given the distinct electromagnetic properties of near-field communications, we present a range of channel models to demonstrate the benefits of XL-MIMO. We further discuss and summarize signal processing schemes for XL-MIMO. It is worth noting that the low-complexity signal processing schemes and deep learning empowered signal processing schemes are reviewed and highlighted to promote the practical implementation of XL-MIMO. Furthermore, we explore the interplay between XL-MIMO and other emergent 6G technologies. Finally, we outline several compelling research directions for future XL-MIMO wireless communication systems. Copyright © 2023, The Authors. All rights reserved.

关键词： MIMO systems

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Integrated Pockels Laser

arXiv

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arXiv 2022年

作者： Li, Mingxiao Chang, Lin Wu, Lue Staffa, Jeremy Ling, Jingwei Javid, Usman A. He, Yang Lopez-Rios, Raymond Xue, Shixin Morin, Theodore J. Shen, Boqiang Wang, Heming Zeng, Siwei Zhu, Lin Vahala, Kerry J. Bowers, John E. Lin, Qiang Department of Electrical and Computer Engineering University of Rochester RochesterNY14627 United States Department of Electrical and Computer Engineering University of California Santa Barbara Santa BarbaraCA93106 United States T. J. Watson Laboratory of Applied Physics California Institute of Technology PasadenaCA91125 United States Institute of Optics University of Rochester RochesterNY14627 United States Department of Electrical and Computer Engineering Center for Optical Materials Science and Engineering Technologies Clemson University ClemsonSC29634 United States

The development of integrated semiconductor lasers has miniaturized traditional bulky laser systems, enabling a wide range of photonic applications. A progression from pure III-V based lasers to III-V/external cavity structures has harnessed low-loss waveguides in different material systems, leading to significant improvements in laser coherence and stability. Despite these successes, however, key functions remain absent. In this work, we address a critical missing function by integrating the Pockels effect into a semiconductor laser. Using a hybrid integrated III-V/Lithium Niobate structure, we demonstrate several essential capabilities that have not existed in previous integrated lasers. These include a record-high frequency modulation speed of 2 exahertz/s (2.0×1018 Hz/s) and fast switching at 50 MHz, both of which are made possible by integration of the electro-optic effect. Moreover, the device co-lases at infrared and visible frequencies via the second-harmonic frequency conversion process, the first such integrated multi-color laser. Combined with its narrow linewidth and wide tunability, this new type of integrated laser holds promise for many applications including LiDAR, microwave photonics, atomic physics, and AR/VR. © 2022, CC BY.

关键词： Semiconductor lasers

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Faithful quantum teleportation via a nanophotonic nonlinear Bell state analyzer

arXiv

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arXiv 2024年

作者： Akin, Joshua Zhao, Yunlei Kwiat, Paul G. Goldschmidt, Elizabeth A. Fang, Kejie Holonyak Micro and Nanotechnology Laboratory Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States Illinois Quantum Information Science and Technology Center University of Illinois at Urbana-Champaign UrbanaIL61801 United States Department of Physics University of Illinois at Urbana-Champaign UrbanaIL61801 United States

Quantum networking protocols, including quantum teleportation and entanglement swapping, use linear-optical Bell state measurements for heralding the distribution and transfer of quantum information. However, a linear-optical Bell state measurement requires identical photons and is susceptible to errors caused by multiphoton emission, fundamentally limiting the efficiency and fidelity of quantum networking protocols. Here we show a nonlinear Bell state analyzer for time-bin encoded photons based on a nanophotonic cavity with efficient sum-frequency generation to filter multiphoton emissions, and utilize it for faithful quantum teleportation involving spectrally distinct photons with fidelities ≥ 94% down to the single-photon level. Our result demonstrates that nonlinear-optical entangling operations, empowered by our efficient nanophotonics platform, can realize faithful quantum information protocols without requiring identical photons and without the fundamental limit on the efficiency and fidelity of a Bell state measurement imposed by linear optics, which facilitates the realization of practical quantum networks. Copyright © 2024, The Authors. All rights reserved.

关键词： Nanophotonics

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STAR-RIS Assisted Covert Wireless Communications with Randomly Distributed Blockages

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IEEE Transactions on Wireless Communications 2025年第6期24卷 4690-4705页

作者： Li, Xingwang Zhao, Jingwei Chen, Gaojie Hao, Wanming Da Costa, Daniel Benevides Nallanathan, Arumugam Shin, Hyundong Henan Polytechnic University School of Physics and Electronic Information Engineering Jiaozuo454099 China Southeast University National Mobile Communications Research Laboratory Nanjing210096 China Shenzhen518107 China 5GIC 6GIC University of Surrey United Kingdom Zhengzhou University School of Electrical and Information Engineering Zhengzhou450001 China King Fahd University of Petroleum and Minerals Interdisciplinary Research Center for Communication Systems and Sensing Department of Electrical Engineering Dhahran31261 Saudi Arabia Queen Mary University of London School of Electronic Engineering and Computer Science London United Kingdom Kyung Hee University Department of Electronic Engineering Yongin-si17104 Korea Republic of Kyung Hee University Department of Electronics and Information Convergence Engineering Korea Republic of Nanyang Technological University School of Electrical and Electronics Engineering 639798 Singapore

As one of the promising technologies, reconfigurable intelligent surface (RIS) and simultaneous transmitting and reflecting RIS (STAR-RIS) have attracted great interest. However, the existing RISs offer broadband tuning capability without filtering function due to the absence of radio frequency (RF) units, which easily leads to the unexpected tuning of the RIS undesired signals, especially in large-scale deployments. For the target network, it is difficult to obtain the parameter settings of RISs to serve other networks, which causes the unpredictability of the wireless environment. In this paper, we consider the covert communication in a STAR-RIS assisted random wireless network with randomly distributed blockages. We investigate the impact of STAR-RIS large-scale deployment on covert communication and leverage its inherent unpredictability for improving the covertness. We derive the average detection error probability for warden within the random wireless networks. Furthermore, we optimize the passive beamforming of STAR-RIS to maximize the covert communication rate, considering both direct and indirect line-of-sight (LoS) links. To address this, we employ an alternating optimization (AO) algorithm based on the semi-definite programming (SDP) method. Finally, numerical results demonstrate significant enhancements and increase covert capability achieved through the large-scale deployment of STAR-RIS. 2002-2012 IEEE.

关键词： Numerical methods

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Fiber-optic nonlinear wavelength converter for adaptive femtosecond biophotonics

arXiv

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arXiv 2023年

作者： Wang, Geng Shi, Jindou Iyer, Rishyashring R. Sorrells, Janet E. Tu, Haohua Beckman Institute for Advanced Science and Technology University of Illinois at Urbana-Champaign UrbanaIL61801 United States Department of Electrical and Computer Engineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States Department of Bioengineering University of Illinois at Urbana-Champaign UrbanaIL61801 United States

Broad and safe access to ultrafast laser technology has been hindered by the absence of optical fiber-delivered pulses with tunable central wavelength, pulse repetition rate, and pulse width in the picosecond-femtosecond regime. To address this long-standing obstacle, we developed a reliable accessory for femtosecond ytterbium fiber chirped pulse amplifiers, termed as fiber-optic nonlinear wavelength converter (FNWC), as an adaptive optical source for the emergent field of femtosecond biophotonics. This accessory embowers the fixed-wavelength laser to produce fiber delivered ~20 nJ pulses with central wavelength across 950-1150 nm, repetition rate across 1-10 MHz, and pulse width across 40-400 fs, with a long-term stability of >2000 hrs. As a prototypical label-free application in biology and medicine, we demonstrate the utility of FNWC in real-time intravital imaging synergistically integrated with modern machine learning and large-scale fluorescence lifetime imaging microscopy. © 2023, CC BY.

关键词： Nonlinear optics

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Emergent Hidden Multipolar State in the Triangular Lattice Magnet TmZn2GaO5

arXiv

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arXiv 2025年

作者： Ennis, Matthew Bag, Rabindranath Cookmeyer, Tessa Stone, Matthew B. Kolesnikov, Alexander I. Hong, Tao Balents, Leon Haravifard, Sara Department of Physics Duke University DurhamNC United States Kavli Institute for Theoretical Physics University of California Santa BarbaraCA United States Neutron Scattering Division Oak Ridge National Laboratory Oak RidgeTN United States Department of Mechanical Engineering and Materials Science Duke University DurhamNC United States Department of Electrical and Computer Engineering Duke University DurhamNC United States

TmZn2GaO5 is a newly synthesized triangular lattice magnet that exhibits a unique quantum phase characterized by strong Ising anisotropy, a pseudo-doublet crystal electric field ground state, and a low-energy gapped excitation at the K point. Unlike its well-known counterparts, TmMgGaO4 and YbMgGaO4, this material crystallizes in a distinct hexagonal structure, leading to a cleaner platform for investigating frustrated magnetism. Magnetic susceptibility, heat capacity, and inelastic neutron scattering measurements confirm the absence of long-range magnetic order down to 50 mK, placing TmZn2GaO5 in a distinct region of the transverse-field Ising model phase diagram. Theoretical calculations based on spin-wave theory and mean-field modeling reproduce key experimental observations, reinforcing the material’s placement in a quantum disordered/multipolar state. These results highlight its potential for exploring quantum disordered states, anisotropic excitations, and exotic quantum phases in frustrated spin systems. Copyright © 2025, The Authors. All rights reserved.

关键词： Magnetic susceptibility

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Quantum Emitters in Aluminum Nitride Induced by Zirconium Ion Implantation

arXiv

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arXiv 2024年

作者： Senichev, Alexander Martin, Zachariah O. Wang, Yongqiang Matthiessen, Owen M. Lagutchev, Alexei Htoon, Han Boltasseva, Alexandra Shalaev, Vladimir M. Elmore Family School of Electrical and Computer Engineering Birck Nanotechnology Center and Purdue Quantum Science and Engineering Institute Purdue University 610 Purdue Mall West LafayetteIN47907 United States Quantum Science Center Department of Energy A National Quantum Information Science Research Center of the U.S Oak Ridge National Laboratory 1 Bethel Valley Road Oak RidgeTN37830 United States

The integration of solid-state single-photon sources with foundry-compatible photonic platforms is crucial for practical and scalable quantum photonic applications. This study investigates aluminum nitride (AlN) as a material with properties highly suitable for integrated on-chip photonics specifically due to AlN capacity to host defect-center related single-photon emitters. We conduct a comprehensive study of the creation and photophysical properties of single-photon emitters in AlN utilizing Zirconium (Zr) and Krypton (Kr) heavy ion implantation and thermal annealing techniques. Guided by theoretical predictions, we assess the potential of Zr ions to create optically addressable spin-defects and employ Kr ions as an alternative approach that targets lattice defects without inducing chemical doping effects. With the 532 nm excitation wavelength, we found that single-photon emitters induced by ion implantation are primarily associated with vacancy-type defects in the AlN lattice for both Zr and Kr ions. The emitter density increases with the ion fluence, and there is an optimal value for the high density of emitters with low AlN background fluorescence. Additionally, under shorter excitation wavelength of 405 nm, Zr-implanted AlN exhibits isolated point-like emitters, which can be related to Zr-based defect complexes. This study provides important insights into the formation and properties of single-photon emitters in aluminum nitride induced by heavy ion implantation, contributing to the advancement of the aluminum nitride platform for on-chip quantum photonic applications. © 2024, CC BY.

关键词： Aluminum nitride

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Efficient, High-purity, Robust Sound Frequency Conversion with a Linear Metasurface

arXiv

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arXiv 2022年

作者： Hu, Chengbo Wang, Wei Ni, Jincheng Ding, Yujiang Weng, Jingkai Liang, Bin Qiu, Cheng-Wei Cheng, Jianchun Key Laboratory of Modern Acoustics MOE Institute of Acoustics Department of Physics Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore

The intrinsic limitation of the material nonlinearity inevitably results in the poor mode purity, conversion efficiency and real-time reconfigurability of the generated harmonic waves, both in optics and acoustics. Rotational Doppler effect provides us an intuitive paradigm to shifting the frequency in a linear system, which needs to be facilitated by a spiraling phase change upon the wave propagation. Here we numerically and experimentally present a rotating linear vortex metasurface and achieve close-to-unity mode purity (above 95%) and conversion efficiency (above 65%) in audible sound frequency as low as 3000 Hz. The topological charge of the transmitted sound is almost immune from the rotational speed and transmissivity, demonstrating the mechanical robustness and stability in adjusting the high-performance frequency conversion in situ. These features enable us to cascade multiple vortex metasurfaces to further enlarge and diversify the extent of sound frequency conversion, which are experimentally verified. Our strategy takes a step further towards the freewheeling sound manipulation at acoustic frequency domain, and may have far-researching impacts in various acoustic communications, signal processing, and contactless detection. Copyright © 2022, The Authors. All rights reserved.

关键词： Vortex flow

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Microheater hotspot engineering for repeatable multi-level switching in foundry-processed phase change silicon photonics

arXiv

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arXiv 2024年

作者： Sun, Hongyi Lian, Chuanyu Vásquez-Aza, Francis Kari, Sadra Rahimi Huang, Yi-Siou Restelli, Alessandro Vitale, Steven A. Takeuchi, Ichiro Hu, Juejun Youngblood, Nathan Pavlidis, Georges Ríos Ocampo, Carlos A. Department of Materials Science & Engineering University of Maryland College ParkMD20742 United States Institute for Research in Electronics and Applied Physics University of Maryland College ParkMD20742 United States Department of Mechanical Engineering University of Connecticut StorrsCT06269 United States Electrical & Computer Engineering Department The University of Pittsburgh PittsburghPA15213 United States Joint Quantum Institute Department of Physics University of Maryland College ParkMD20742 United States Advanced Materials and Microsystems Group MIT Lincoln Laboratory LexingtonMA02139 United States Department of Materials Science & Engineering MIT CambridgeMA02139 United States

Nonvolatile photonic integrated circuits employing phase change materials have relied either on optical switching mechanisms with precise multi-level control but poor scalability or electrical switching with seamless integration and scalability but mostly limited to a binary response. Recent works have demonstrated electrical multi-level switching;however, they relied on the stochastic nucleation process to achieve partial crystallization with low demonstrated repeatability and cyclability. Here, we re-engineer waveguide-integrated microheaters to achieve precise spatial control of the temperature profile (i.e., hotspot) and, thus, switch deterministic areas of an embedded phase change material cell. We experimentally demonstrate this concept using a variety of foundry-processed doped-silicon microheaters on a silicon-on-insulator platform to trigger multi-step amorphization and reversible switching of Sb2Se3 and Ge2Sb2Se4Te alloys. We further characterize the response of our microheaters using Transient Thermoreflectance Imaging. Our approach combines the deterministic control resulting from a spatially resolved glassy-crystalline distribution with the scalability of electro-thermal switching devices, thus paving the way to reliable multi-level switching towards robust reprogrammable phase-change photonic devices for analog processing and computing. © 2024, CC BY-NC-SA.

关键词： Scalability

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Multi-Agent Reinforcement Learning in Wireless Distributed Networks for 6G

arXiv

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arXiv 2025年

作者： Zhang, Jiayi Liu, Ziheng Zhu, Yiyang Shi, Enyu Xu, Bokai Yuen, Chau Niyato, Dusit Debbah, Mérouane Jin, Shi Ai, Bo Shen, Xuemin School of Electronic and Information Engineering The Frontiers Science Center for Smart High-Speed Railway System Beijing jiaotong University Beijing100044 China School of Electrical and Electronics Engineering Nanyang Technological University 639798 Singapore College of Computing and Data Science Nanyang Technological University 639798 Singapore KU 6G Research Center Department of Computer and Information Engineering Khalifa University Abu Dhabi127788 United Arab Emirates CentraleSupelec University Paris-Saclay Gif-sur-Yvette91192 France National Mobile Communications Research Laboratory Southeast University Nanjing210096 China Department of Electrical and Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada

The introduction of intelligent interconnectivity between the physical and human worlds has attracted great attention for future sixth-generation (6G) networks, emphasizing massive capacity, ultra-low latency, and unparalleled reliability. Wireless distributed networks and multi-agent reinforcement learning (MARL), both of which have evolved from centralized paradigms, are two promising solutions for the great attention. Given their distinct capabilities, such as decentralization and collaborative mechanisms, integrating these two paradigms holds great promise for unleashing the full power of 6G, attracting significant research and development attention. This paper provides a comprehensive study on MARL-assisted wireless distributed networks for 6G. In particular, we introduce the basic mathematical background and evolution of wireless distributed networks and MARL, as well as demonstrate their interrelationships. Subsequently, we analyze different structures of wireless distributed networks from the perspectives of homogeneous and heterogeneous. Furthermore, we introduce the basic concepts of MARL and discuss two typical categories, including model-based and model-free. We then present critical challenges faced by MARL-assisted wireless distributed networks, providing important guidance and insights for actual implementation. We also explore an interplay between MARL-assisted wireless distributed networks and emerging techniques, such as information bottleneck and mirror learning, delivering in-depth analyses and application scenarios. Finally, we outline several compelling research directions for future MARL-assisted wireless distributed networks. Copyright © 2025, The Authors. All rights reserved.

关键词： Adversarial machine learning

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