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
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
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
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
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 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.
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.
