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Conference on Lasers and Electro-Optics (CLEO)

作者： Niloy Acharjee Hongyi Sun Siddhartha Ghosh Carlos A. Ríos Ocampo Institute for Research in Electronics & Applied Physics University of Maryland College Park MD USA Department of Electrical & Computer Engineering University of Maryland College Park MD USA Department of Materials Science & Engineering University of Maryland College Park MD USA Space Systems - Northrop Grumman 1 Space Park Blvd Redondo Beach CA USA

We demonstrate a monolithic Ge2Sb2Se4Te platform for tunable photonic integrated circuits. We fabricated and measured various on-chip components, including waveguides with preliminary 55.7±3.65 dB/cm propagation ... 详细信息

ISBN: (纸本)9798350369311

关键词： Phase change materials Waveguide components Refractive index Photonic integrated circuits Crystallization Propagation losses System-on-chip Electro-optical waveguides Optimization Photonics

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Miniaturizing Ultrastable Electromagnetic Oscillators: Sub-10−14 Frequency Instability from a Centimeter-Scale Fabry-Perot Cavity

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Physical Review applied 2022年第5期18卷 054054-054054页

作者： Charles A. McLemore Naijun Jin Megan L. Kelleher James P. Hendrie David Mason Yizhi Luo Dahyeon Lee Peter Rakich Scott A. Diddams Franklyn Quinlan Department of Physics University of Colorado Boulder Boulder Colorado 80309 USA National Institute of Standards and Technology Boulder Colorado 80305 USA Department of Applied Physics Yale University New Haven Connecticut 06520 USA Department of Electrical Computer and Energy Engineering University of Colorado Boulder Boulder Colorado 80309 USA

The best performance from compact, portable, and repeatably manufactured electromagnetic (EM) oscillators has for decades been built upon crystalline quartz resonators operating at radio frequencies. Such a source of frequency-stable EM waves has enabled a wide range of applications of significant technical and societal benefit, such as navigation and communication systems, distributed sensing, geodesy, and fundamental physics. However, meeting demands for increased measurement sensitivity requires pushing beyond a fractional frequency stability of 10−13, typical of the best ovenized quartz. To date, such performance has been available in the microwave domain only with the use of complex cryogenic systems, or in the optical domain at the expense of larger volume and weight. In either case, the size, weight, and power of state-of-the-art EM oscillators has relegated their use to laboratory experiments. Here we demonstrate the validity of a manufacturable, compact Fabry-Perot reference that improves upon all other centimeter-scale oscillators by more than a factor of 10, including those based on solid-state optical resonators as well as quartz. In a specific implementation, we show an 8 ml bonded assembly containing three vacuum-gap Fabry-Perot optical cavities with mirrors lithographically fabricated on a single substrate, each with quality factor exceeding 10 billion. A laser stabilized to one of the cavities exhibits thermal-noise-limited phase noise for offset frequencies ranging from 1 Hz to nearly 1 kHz, and fractional frequency stability of 7×10−15 at 1 s. Our advance with lithographically defined and microfabricated mirrors is validated by rigorous models, which highlight a path to oscillators with size comparable to ovenized quartz, but with significantly improved performance. For example, we predict sub-10−14 performance is readily attainable with a Fabry-Perot cavity volume less than 2 ml.

关键词： Atomic, optical & lattice clocks Laser applications Metrology Optical microcavities Optical sources & detectors Time & frequency standards Cavity resonators RF, microwave, & terahertz sources

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Unavoidable multilevel biaxial symmetry breaking in chiral hybrid liquid crystals

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Physical Review E 2025年第4期111卷 045410-045410页

作者： Jin-Sheng Wu Marina Torres Lázaro Souvik Ghosh Haridas Mundoor Henricus H. Wensink Ivan I. Smalyukh Department of Physics and Chemical Physics Program University of Colorado Boulder Colorado 80309 USA Laboratoire de Physique des Solides–UMR 8502 Université Paris-Saclay and CNRS 91405 Orsay France International Institute for Sustainability with Knotted Chiral Meta Matter Hiroshima University Higashihiroshima Japan Department of Electrical Computer and Energy Engineering Materials Science and Engineering Program and Soft Materials Research Center University of Colorado Boulder Colorado 80309 USA Renewable and Sustainable Energy Institute National Renewable Energy Laboratory and University of Colorado Boulder Colorado 80309 USA

Chiral nematic or cholesteric liquid crystals (LCs) are fluid mesophases with long-ranged orientational order featuring a quasilayered periodicity imparted by a helical director configuration but lacking long-range positional order. Doping molecular cholesteric LCs with strongly anisotropic uniaxial colloidal particles adds another level of complexity because of the interplay between weak surface-anchoring boundary conditions and bulk-based elastic distortions near the particle-LC interface. Using cylindrical colloidal disks and rods with different geometric shapes and surface conditions, we demonstrate that these colloidal inclusions generically exhibit biaxial orientational probability distributions which may impart anomalously strong local biaxiality onto the hybrid cholesteric LC structure. Unlike nonchiral hybrid molecular-colloidal LCs, where biaxial order emerges only at critical colloid volume fractions exceeding some uniaxial-biaxial transition value, the orientational probability of the colloidal inclusions immersed in chiral nematic hosts is unambiguously biaxial even at infinite dilution. We demonstrate that the colloids induce local biaxial perturbations within the molecular orientational order of the LC host medium which strongly enhances the weak but native biaxial order of chiral nematic LC induced by the chiral symmetry breaking of the director field. With the help of analytical modeling and computer simulations based on the Landau–de Gennes free energy of the host LC around the colloids, we rationalize the observed multilevel biaxial order and conclude that it is not only unavoidable but also strongly enhanced compared to both achiral hybrid LCs and purely molecular cholesteric LCs.

关键词： Cholesteric liquid crystals

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Qudit Dynamical Decoupling on a Superconducting Quantum Processor

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Physical Review Letters 2025年第5期134卷 050601-050601页

作者： Vinay Tripathi Noah Goss Arian Vezvaee Long B. Nguyen Irfan Siddiqi Daniel A. Lidar Department of Physics and Astronomy University of Southern California Los Angeles California 90089 USA Center for Quantum Information Science and Technology University of Southern California Los Angeles California 90089 USA Quantum Nanoelectronics Laboratory Department of Physics University of California at Berkeley Berkeley California 94720 USA Applied Math and Computational Research Division Lawrence Berkeley National Lab Berkeley California 94720 USA Department of Electrical and Computer Engineering University of Southern California Los Angeles California 90089 USA Department of Chemistry University of Southern California Los Angeles California 90089 USA

Multilevel qudit systems are increasingly being explored as alternatives to traditional qubit systems due to their denser information storage and processing potential. However, qudits are more susceptible to decoherence than qubits due to increased loss channels, noise sensitivity, and crosstalk. To address these challenges, we develop protocols for dynamical decoupling (DD) of qudit systems based on the Heisenberg-Weyl group. We implement and experimentally verify these DD protocols on a superconducting transmon processor that supports qudit operation based on qutrits (d=3) and ququarts (d=4). Specifically, we demonstrate single-qudit DD sequences to decouple qutrits and ququarts from system-bath-induced decoherence. We also introduce two-qudit DD sequences designed to suppress the detrimental cross-Kerr couplings between coupled qudits. This allows us to demonstrate a significant improvement in the fidelity of time-evolved qutrit Bell states. Our results highlight the utility of leveraging DD to enable scalable qudit-based quantum computing.

关键词： Qubits

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Ultrastable vacuum-gap Fabry-Pérot cavities operated in air

arXiv

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arXiv 2024年

作者： Liu, Yifan Jin, Naijun Lee, Dahyeon McLemore, Charles Nakamura, Takuma Kelleher, Megan Cheng, Haotian Schima, Susan Hoghooghi, Nazanin Diddams, Scott Rakich, Peter Quinlan, Franklyn Department of Physics University of Colorado Boulder BoulderCO80309 United States Time and Frequency Division National Institute of Standards and Technology BoulderCO80305 United States Department of Applied Physics Yale University New HavenCT06520 United States Electrical Computer & Energy Engineering University of Colorado Boulder BoulderCO80309 United States

We demonstrate a vacuum-gap ultrastable optical reference cavity that does not require a vacuum enclosure. Our simple method of optical contact bonding in a vacuum environment allows for cavity operation in air while maintaining vacuum between the cavity mirrors. Vacuum is maintained long term, with no observed degradation in cavity stability for over 1 year after bonding. For a 1550 nm laser stabilized to a 9.7 mL in-vacuum bonded cavity, the measured Allan deviation is 2.4 × 10−14 at 1 s and its phase noise is thermal-noise-limited from 0.1 Hz to 10 kHz, reaching about -105 dBc/Hz at 10 kHz offset frequency. This represents the highest stability of any oscillator operated without a vacuum enclosure. Furthermore, we demonstrate a 0.5 mL in-vacuum bonded cavity created using microfabricated mirrors and cavity dicing, with phase noise reaching -95 dBc/Hz at 10 kHz offset frequency. By relieving the need for high-vacuum enclosures, we greatly enhance the portability and utility of low noise, compact cavity-stabilized lasers, with applications ranging from environmental sensing to mobile optical clocks to ultralow noise microwave generation. © 2024, CC BY.

关键词： Cavity resonators

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Quantum permutation puzzles with indistinguishable particles

arXiv

引用

arXiv 2024年

作者： Lordi, Noah Trank-Greene, Maedée Kyle, Akira Combes, Joshua Department of Physics University of Colorado Boulder 2000 Colorado Ave BoulderCO80309 United States Department of Applied Mathematics University of Colorado Boulder BoulderCO80309 United States Electrical Computer and Energy Engineering University of Colorado Boulder BoulderCO80309 United States Schools of Physics and Mathematics University of Melbourne VIC3010 Australia

Permutation puzzles, such as the Rubik’s cube and the 15 puzzle, are enjoyed by the general public and mathematicians alike. Here we introduce quantum versions of permutation puzzles where the pieces of the puzzles are replaced with indistinguishable quantum particles. The moves in the puzzle are achieved by swapping or permuting the particles. We show that simply permuting the particles can be mapped to a classical permutation puzzle, even though the identical particles are entangled. However, we obtain a genuine quantum puzzle by adding a quantum move—the square root of SWAP. The resulting puzzle cannot be mapped to a classical permutation puzzle. We focus predominately on the quantization of the 2 × 2 slide puzzle and briefly treat the 2 × 2 × 1 Rubik’s cube. © 2024, CC BY.

关键词： Quantum entanglement

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Dynamic transformation between a skyrmion string and a bimeron string in a layered frustrated system

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Physical Review B 2021年第22期104卷 L220406-L220406页

作者： Xichao Zhang Jing Xia Oleg A. Tretiakov Hung T. Diep Guoping Zhao Jinbo Yang Yan Zhou Motohiko Ezawa Xiaoxi Liu Department of Electrical and Computer Engineering Shinshu University 4-17-1 Wakasato Nagano 380-8553 Japan School of Science and Engineering The Chinese University of Hong Kong Shenzhen Guangdong 518172 China School of Physics The University of New South Wales Sydney 2052 Australia Laboratoire de Physique Théorique et Modélisation CY Cergy Paris Université 95302 Cergy-Pontoise Cedex France College of Physics and Electronic Engineering Sichuan Normal University Chengdu 610068 China State Key Laboratory for Mesoscopic Physics School of Physics Peking University Beijing 100871 China Department of Applied Physics The University of Tokyo 7-3-1 Hongo Tokyo 113-8656 Japan

Frustrated topological spin textures have unique properties that may enable novel spintronic applications, such as helicity-based information storage and computing. Here, we report the statics and current-induced dynamics of two-dimensional (2D) pancake skyrmions in a stack of weakly coupled frustrated magnetic monolayers, which form a three-dimensional (3D) skyrmion string. The Bloch-type skyrmion string is energetically more stable than its Néel-type counterpart. It can be driven into translational motion by the dampinglike spin-orbit torque and shows the damping-dependent skyrmion Hall effect. Most notably, the skyrmion string can be transformed to a dynamically stable bimeron string by the dampinglike spin-orbit torque. The current-induced bimeron string rotates stably with respect to its center, which can spontaneously transform back to a skyrmion string when the current is switched off. Our results reveal unusual physical properties of 3D frustrated spin textures, and may open up different possibilities for spintronic applications based on skyrmion and bimeron strings.

关键词： Frustrated magnetism Magnetism Skyrmions Spintronics

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AI-Enabled Jammer Deception Using Decoy Packets

AI-Enabled Jammer Deception Using Decoy Packets

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GLOBECOM 2022 - 2022 IEEE Global Communications Conference

作者： Stephan Frisbie Mohamed Younis The Johns Hopkins University Applied Physics Laboratory Laurel Maryland Department of Computer Science and Electrical Engineering University of Maryland Baltimore County Baltimore Maryland United States

ISBN: (纸本)9781665435413

In this work, we present a learning algorithm for a wireless communications network to transmit decoy packets to counter an adversarial sensing-reactive jammer. As the jammer is required to search across channels for data transmissions, decoy packets can have the effect of stalling the jammer on a particular channel, preventing it from continuing its search and leaving legitimate packets unimpeded. A reinforcement learning algorithm trains a deep neural network with an exploration-exploitation algorithm and experience replay. The state- and action-space and reward function are presented as components of the reinforcement learning framework. Our algorithm is tested with software simulations, modeling ZigBee communications nodes using time-division multiple access for medium access control. A reactive jammer is modeled in the simulation, with the goal of disrupting any detected ZigBee transmissions. A means to measure and distribute the reward function and system state to enable edge-learning in this context is presented as part of the implementation. The results demonstrate the effectiveness of our algorithm in mitigating the jamming attack, outperforming a random decoy strategy by a factor of two.

关键词： Wireless communication Wireless sensor networks Software algorithms Zigbee Reinforcement learning Throughput Software

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Terahertz Landau Polaritons in Nano-slots: Ultrastrong Coupling under Extreme Spatial Confinement

Terahertz Landau Polaritons in Nano-slots: Ultrastrong Coupl...

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International Conference on Infrared and Millimeter Waves

作者： Dasom Kim Sunghwan Kim Dukhyung Lee Shuang Liang Fuyang Tay Michael J. Manfra Dai-Sik Kim Junichiro Kono Department of Electrical and Computer Engineering Rice University Houston TX USA Applied Physics Graduate Program Smalley-Curl Institute Rice University Houston TX USA Department of Physics Long-wavelength Nanotechnology Laboratory and Quantum Photonics Institute Ulsan National Institute of Science and Technology (UNIST) Ulsan South Korea Department of Physics and Astronomy Purdue University West Lafayette IN USA Birck Nanotechnology Center Purdue University West Lafayette IN USA Elmore Family School of Electrical and Computer Engineering Purdue University West Lafayette IN USA School of Materials Engineering Purdue University West Lafayette IN USA Department of Physics and Astronomy Rice University Houston TX USA Department of Material Science and NanoEngineering Rice University Houston TX USA

We report ultrastrong coupling of the cyclotron resonance of a two-dimensional electron gas in a GaAs quantum well to terahertz cavity photons under extreme confinement to the nanometer scale. This was realized by an array of nano-slots fabricated close to the quantum well layer on the GaAs substrate. Our terahertz magnetospectroscopic measurements revealed two polariton branches as a function of applied magnetic field. While the photon-like part of the two polariton branches was clearly observed, the matter-like part was generally elusive. Our electromagnetic simulations quantitatively reproduce our observation for the upper-polariton branch. However, for the lower-polariton branch, our simulations predict a pronounced resonance, which was absent in experimental spectra. This discrepancy may be a consequence of the breakdown of the dipole approximation in this extreme confinement situation.

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Analysis of high-power packages for white-light-emitting diode lamps with remote phosphor

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MRS Online Proceedings Library 2021年第1期892卷 166-171页

作者： Hong Luo Jong Kyu Kim Yangang Xi E. Fred Schubert Jaehee Cho Cheolsoo Sone Yongjo Park Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy USA Electrical Computer and Systems Engineering Department Rensselaer Polytechnic Institute Troy USA Photonics Program Team Samsung Advanced Institute of Technology Suwon Korea

An optimized packaging configuration for high-power white-light-emitting diode (LED) lamps that employs a diffuse reflector cup, a remote phosphor and a hemi-spherically-shaped encapsulation is presented. Ray tracing simulations for this configuration show that the phosphor efficiency can be enhanced by up to 50% over conventional packages. It is experimentally shown that dichromatic LED lamps with remote phosphor and diffuse reflector cup configuration have higher phosphor efficiency by 15.4% for blue-pumped yellow phosphor and by 27% for ultraviolet-pumped blue phosphor over conventional packages. Those improvements are attributed to reduced absorption of the phosphorescence by the LED chip and the reduction of deterministic optical modes trapped inside the encapsulant.

关键词： packaging optoelectronic optical properties

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