A distant-neighbor quantum-mechanical method is used to study the nonlinear optical wave mixing in graphene nanoflakes(GNFs),including sum-and difference-frequency generation,as well as four-wave mixing.Our analysis s...A distant-neighbor quantum-mechanical method is used to study the nonlinear optical wave mixing in graphene nanoflakes(GNFs),including sum-and difference-frequency generation,as well as four-wave mixing.Our analysis shows that molecular-scale GNFs support quantum plasmons in the visible spectrum region,and significant enhancement of nonlinear optical wave mixing is achieved.Specifically,the second-and third-order wave-mixing polarizabilities of GNFs are dramatically enhanced,provided that one(or more) of the input or output frequencies coincide with a quantum plasmon resonance.Moreover,by embedding a cavity into hexagonal GNFs,we show that one can break the structural inversion symmetry and enable otherwise forbidden second-order wave mixing,which is found to be enhanced by the quantum plasmon resonance too.This study reveals that the molecular-sized graphene could be used in the quantum regime for nanoscale nonlinear optical devices and ultrasensitive molecular sensors.展开更多
Topological pumping refers to transfer of a physical quantity governed by the system topology,resulting in quantized amounts of the transferred quantities.It is a ubiquitous wave phenomenon typically considered subjec...Topological pumping refers to transfer of a physical quantity governed by the system topology,resulting in quantized amounts of the transferred quantities.It is a ubiquitous wave phenomenon typically considered subject to exactly periodic adiabatic variation of the system parameters.Recently,proposals for generalizing quasi-periodic topological pumping and identifying possible physical settings for its implementation have emerged.In a strict sense,pumping with incommensurate frequencies can only manifest over infinite evolution distances,raising a fundamental question about its observability in real-world finite-dimensional systems.Here we demonstrate that bi-chromatic topological pumping with two frequencies,whose ratio is an irrational number,can be viewed as the convergence limit of pumping with two commensurate frequencies representing the best rational approximations of that irrational number.In our experiment,this phenomenon is observed as the displacement of a light beam center in photorefractive crystals induced by two optical lattices.The longitudinal periods of the lattices,that in the paraxial approximation emulate two pumping frequencies,are related as Fibonacci numbers,successively approaching the golden ratio.We observed that a one-cycle displacement of the beam center at each successive approximation is determined by the relation between successive Fibonacci numbers,while the average direction of propagation(emulating average pumping velocity)of the beam is determined by the golden ratio.展开更多
Optical neural networks present distinct advantages over traditional electrical counterparts,such as accelerated data processing and reduced energy consumption.While coherent light is conventionally used in optical ne...Optical neural networks present distinct advantages over traditional electrical counterparts,such as accelerated data processing and reduced energy consumption.While coherent light is conventionally used in optical neural networks,our study proposed harnessing spatially incoherent light in all-optical Fourier neural networks.Contrary to natural predictions of declining target recognition accuracy with increased incoherence,our experimental results demonstrated a surprising outcome:improved accuracy with incoherent light.We attribute this enhancement to spatially incoherent light’s ability to alleviate experimental errors like diffraction rings and laser speckle.Our experiments introduced controllable spatial incoherence by passing monochromatic light through a spatial light modulator featuring a dynamically changing random phase array.These findings underscore partially coherent light’s potential to optimize optical neural networks,delivering dependable and efficient solutions for applications demanding consistent accuracy and robustness across diverse conditions,including on-chip optical computing,photonic interconnects,and reconfigurable optical processors.展开更多
Efficient and trusted regulation of unmanned aerial vehicles(UAVs)is an essential but challenging issue in the future era of the Internet of Low-altitude Intelligence,due to the difficulties in UAVs'identity recog...Efficient and trusted regulation of unmanned aerial vehicles(UAVs)is an essential but challenging issue in the future era of the Internet of Low-altitude Intelligence,due to the difficulties in UAVs'identity recognition and location matching,potential for falsified information reporting,etc.To address this challenging issue,in this paper,we propose a blockchain-based UAV location authentication scheme,which employs a distance bounding protocol to establish a location proof,ensuring the authenticity of UAV positions.To preserve the privacy of UAVs,anonymous certificates and zero-knowledge proof are used.The security of the proposed scheme is analyzed.Experiments demonstrate the efficiency and feasibility of the proposed scheme.展开更多
We study the nonlinear optical properties of heterojunctions made of graphene nanoribbons(GNRs)consisting of two segments with either the same or different topological properties.By utilizing a quantum mechanical appr...We study the nonlinear optical properties of heterojunctions made of graphene nanoribbons(GNRs)consisting of two segments with either the same or different topological properties.By utilizing a quantum mechanical approach that incorporates distant-neighbor interactions,we demonstrate that the presence of topological interface states significantly enhances the second-and third-order nonlinear optical response of GNR heterojunctions that are created by merging two topologically inequivalent GNRs.Specifically,GNR heterojunctions with topological interface states display third-order harmonic hyperpolarizabilities that are more than two orders of magnitude larger than those of their similarly sized counterparts without topological interface states,whereas the second-order harmonic hyperpolarizabilities exhibit a more than ten-fold contrast between heterojunctions with and without topological interface states.Additionally,we find that the topological state at the interface between two topologically distinct GNRs can induce a noticeable red-shift of the quantum plasmon frequency of the heterojunctions.Our results reveal a general and profound connection between the existence of topological states and an enhanced nonlinear optical response of graphene nanostructures and possible other photonic systems.展开更多
With the growing utilization of unmanned aerial vehicles(UAVs),low-altitude airspace is becoming increasingly congested,posing significant challenges to Air Traffic Control(ATC).The Automatic Dependent Surveillance-Br...With the growing utilization of unmanned aerial vehicles(UAVs),low-altitude airspace is becoming increasingly congested,posing significant challenges to Air Traffic Control(ATC).The Automatic Dependent Surveillance-Broadcast(ADS-B)system is used to report the location of UAVs.However,due to channel noise and adversarial interference,ADS-B data may be inaccurate.To address this issue,a position estimation method based on Bidirectional Long Short-Term Memory Multi-Layer Perceptron(BiLSTM-MLP)was proposed.In this method,ADS-B signal power is used to estimate the position of UAVs as a baseline approach.Experimental results demonstrate that the BiLSTM-MLP based method significantly improves estimation accuracy.Moreover,a blockchain-based dynamic reputation mechanism,aligned with the position estimation method,was proposed.The mechanism integrates information from the third-party UAV and the location data provided by the UAV itself to dynamically update the credibility of the UAV,and thus achieves decentralized access control of UAVs in low-altitude airspace.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11947007)the Natural Science Foundation of Guangdong Province,China(Grant No.2019A1515011499)the Department of Education of Guangdong Province,China(Grant No.2019KTSCX087)。
文摘A distant-neighbor quantum-mechanical method is used to study the nonlinear optical wave mixing in graphene nanoflakes(GNFs),including sum-and difference-frequency generation,as well as four-wave mixing.Our analysis shows that molecular-scale GNFs support quantum plasmons in the visible spectrum region,and significant enhancement of nonlinear optical wave mixing is achieved.Specifically,the second-and third-order wave-mixing polarizabilities of GNFs are dramatically enhanced,provided that one(or more) of the input or output frequencies coincide with a quantum plasmon resonance.Moreover,by embedding a cavity into hexagonal GNFs,we show that one can break the structural inversion symmetry and enable otherwise forbidden second-order wave mixing,which is found to be enhanced by the quantum plasmon resonance too.This study reveals that the molecular-sized graphene could be used in the quantum regime for nanoscale nonlinear optical devices and ultrasensitive molecular sensors.
基金supported by the Fundacao para a Ciência e Tecnologia under the project 2023.13176.PEX(DOI https://doi.org/10.54499/2023.13176.PEX)by national funds,under the Unit CFTC-Centro de Física Teórica e Computacional,reference UID/00618/2025,financing period 2025–2029+4 种基金funding from the project FFUU-2024-0003 of the Institute of Spectroscopy of the Russian Academy of Sciencesfunding from the Shanghai Outstanding Academic Leaders Plan(No.20XD1402000)Shanghai Leading Talent Program 1 of Eastern Talent Plan(The 16th Shanghai Leading Talent Program)the support of the National Natural Science Foundation of China(No.12404385,No.12304366)China Postdoctoral Science Foundation(No.BX20230217,No.BX20230218,No.2023M742295,No.2024M751950).
文摘Topological pumping refers to transfer of a physical quantity governed by the system topology,resulting in quantized amounts of the transferred quantities.It is a ubiquitous wave phenomenon typically considered subject to exactly periodic adiabatic variation of the system parameters.Recently,proposals for generalizing quasi-periodic topological pumping and identifying possible physical settings for its implementation have emerged.In a strict sense,pumping with incommensurate frequencies can only manifest over infinite evolution distances,raising a fundamental question about its observability in real-world finite-dimensional systems.Here we demonstrate that bi-chromatic topological pumping with two frequencies,whose ratio is an irrational number,can be viewed as the convergence limit of pumping with two commensurate frequencies representing the best rational approximations of that irrational number.In our experiment,this phenomenon is observed as the displacement of a light beam center in photorefractive crystals induced by two optical lattices.The longitudinal periods of the lattices,that in the paraxial approximation emulate two pumping frequencies,are related as Fibonacci numbers,successively approaching the golden ratio.We observed that a one-cycle displacement of the beam center at each successive approximation is determined by the relation between successive Fibonacci numbers,while the average direction of propagation(emulating average pumping velocity)of the beam is determined by the golden ratio.
基金supported in part by the National Natural Science Foundation of China under grant U23B2011。
文摘Optical neural networks present distinct advantages over traditional electrical counterparts,such as accelerated data processing and reduced energy consumption.While coherent light is conventionally used in optical neural networks,our study proposed harnessing spatially incoherent light in all-optical Fourier neural networks.Contrary to natural predictions of declining target recognition accuracy with increased incoherence,our experimental results demonstrated a surprising outcome:improved accuracy with incoherent light.We attribute this enhancement to spatially incoherent light’s ability to alleviate experimental errors like diffraction rings and laser speckle.Our experiments introduced controllable spatial incoherence by passing monochromatic light through a spatial light modulator featuring a dynamically changing random phase array.These findings underscore partially coherent light’s potential to optimize optical neural networks,delivering dependable and efficient solutions for applications demanding consistent accuracy and robustness across diverse conditions,including on-chip optical computing,photonic interconnects,and reconfigurable optical processors.
基金supported in part by the Jiangsu Provincial Key Research and Development Program under Grants BE2022068the National Natural Science Foundation of China under Grant 62371231,62001220+2 种基金the Young Elite Scientist Sponsorship ProgramChina Association for Science and TechnologyYESS20200207
文摘Efficient and trusted regulation of unmanned aerial vehicles(UAVs)is an essential but challenging issue in the future era of the Internet of Low-altitude Intelligence,due to the difficulties in UAVs'identity recognition and location matching,potential for falsified information reporting,etc.To address this challenging issue,in this paper,we propose a blockchain-based UAV location authentication scheme,which employs a distance bounding protocol to establish a location proof,ensuring the authenticity of UAV positions.To preserve the privacy of UAVs,anonymous certificates and zero-knowledge proof are used.The security of the proposed scheme is analyzed.Experiments demonstrate the efficiency and feasibility of the proposed scheme.
基金funding provided by Shanghai Jiao Tong Universitysupported by the National Natural Science Foundation of China(Grant Nos.12104104,62175042)+5 种基金the Natural Science Foundation of Guangdong Province(Grant No.2019A1515011499)the Department of Education of Guangdong Province(Grant No.2019KTSCX087)the Start-up Funding of Guangdong Polytechnic Normal University(Grant No.2021SDKYA165)the Guangdong Department of Education Projects of Improving Scientific Research Capabilities of Key Subjects Construction(Grant No.2022ZDJS016)the European Research Council(ERCGrant No.ERC-2014-CoG-648328).
文摘We study the nonlinear optical properties of heterojunctions made of graphene nanoribbons(GNRs)consisting of two segments with either the same or different topological properties.By utilizing a quantum mechanical approach that incorporates distant-neighbor interactions,we demonstrate that the presence of topological interface states significantly enhances the second-and third-order nonlinear optical response of GNR heterojunctions that are created by merging two topologically inequivalent GNRs.Specifically,GNR heterojunctions with topological interface states display third-order harmonic hyperpolarizabilities that are more than two orders of magnitude larger than those of their similarly sized counterparts without topological interface states,whereas the second-order harmonic hyperpolarizabilities exhibit a more than ten-fold contrast between heterojunctions with and without topological interface states.Additionally,we find that the topological state at the interface between two topologically distinct GNRs can induce a noticeable red-shift of the quantum plasmon frequency of the heterojunctions.Our results reveal a general and profound connection between the existence of topological states and an enhanced nonlinear optical response of graphene nanostructures and possible other photonic systems.
基金This work was supported by the Key Research and Development Program of Jiangsu[grant numbers BE2022068,BE2022068-1].
文摘With the growing utilization of unmanned aerial vehicles(UAVs),low-altitude airspace is becoming increasingly congested,posing significant challenges to Air Traffic Control(ATC).The Automatic Dependent Surveillance-Broadcast(ADS-B)system is used to report the location of UAVs.However,due to channel noise and adversarial interference,ADS-B data may be inaccurate.To address this issue,a position estimation method based on Bidirectional Long Short-Term Memory Multi-Layer Perceptron(BiLSTM-MLP)was proposed.In this method,ADS-B signal power is used to estimate the position of UAVs as a baseline approach.Experimental results demonstrate that the BiLSTM-MLP based method significantly improves estimation accuracy.Moreover,a blockchain-based dynamic reputation mechanism,aligned with the position estimation method,was proposed.The mechanism integrates information from the third-party UAV and the location data provided by the UAV itself to dynamically update the credibility of the UAV,and thus achieves decentralized access control of UAVs in low-altitude airspace.
