None Guan Xing-Yue, None Huang Heng-Yan, None Peng Hua-Qi, None Liu Yan-Hang, None Li Wen-Fei, None Wang Wei
Molecular simulation has already become a powerful tool for investigating life principles at the molecular level. The past 50 years witnessed that molecular simulation has enabled the quantitative characterization of both kinetic and thermodynamic properties of complicated molecular processes, such as protein folding and conformational changes. In recent years, the application of machine learning algorithms represented by deep learning has further advanced the development of molecular simulation. This work provides a review on machine learning methods in molecular simulation, focusing on the important progress made by machine learning algorithms in improving the accuracy of molecular force fields, the efficiency of molecular simulation conformation sampling, and also the processing of high-dimensional simulation data. On this basis, this review gives an outlook for future research based on machine learning techniques to further overcome the accuracy and effciency bottleneck of molecular simulation, expand the scope of molecular simulation, and realize the integration of computational simulation and experimental results.
{"title":"Machine Learning in Molecular Simulations of Biomolecules","authors":"None Guan Xing-Yue, None Huang Heng-Yan, None Peng Hua-Qi, None Liu Yan-Hang, None Li Wen-Fei, None Wang Wei","doi":"10.7498/aps.72.20231624","DOIUrl":"https://doi.org/10.7498/aps.72.20231624","url":null,"abstract":"Molecular simulation has already become a powerful tool for investigating life principles at the molecular level. The past 50 years witnessed that molecular simulation has enabled the quantitative characterization of both kinetic and thermodynamic properties of complicated molecular processes, such as protein folding and conformational changes. In recent years, the application of machine learning algorithms represented by deep learning has further advanced the development of molecular simulation. This work provides a review on machine learning methods in molecular simulation, focusing on the important progress made by machine learning algorithms in improving the accuracy of molecular force fields, the efficiency of molecular simulation conformation sampling, and also the processing of high-dimensional simulation data. On this basis, this review gives an outlook for future research based on machine learning techniques to further overcome the accuracy and effciency bottleneck of molecular simulation, expand the scope of molecular simulation, and realize the integration of computational simulation and experimental results.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135562848","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Zheng Lin-Qi, None Shi Shu-Hua, None Li Jin-Ze, None Wang Zi-Yu, None Li Shuang
As a commonly used food additive, synthetic dyes are widely used in foods such as beverages, sweets and dairy products, and in the food processing process, excessive use of synthetic dyes may induce cell mutations, children's hyperactivity, genetic diseases and even cancer, posing a great threat to human health. As a fast, cheap, stable, ultra-sensitive and accurate detection method, SERS detection can reflect rich molecular fingerprint information through the vibration of the analyte, and accurately determine the trace amount of synthetic dyes in the actual environment. The metal/semiconductor heterostructure formed by the combination of plasmon metal and semiconductor is advantageous for the enhancement of photoinduced charge transfer efficiency (PICT), and has obvious advantages in the study of surface-enhanced Raman scattering. In this paper, the prepared hybrid substrate is annealed to further improve the surface-enhanced Raman scattering activity. Initially, high-density and monodisperse silver/silver oxide (Ag/Ag2O) nanoparticles were loaded onto two-dimensional hexagonal boron nitride (h-BN) nanosheets. On this basis, by annealing the system at high temperature, an efficient charge transfer channel is constructed, which greatly improves the PICT efficiency and chemical enhancement (CM). It was confirmed by experiments that the SERS signal intensity of h-BN/Ag/Ag2O material annealed at 320 ℃ with crystal violet (CV) as probe molecule was significantly increased by 18 times compared with unannealed material，enhancement factor (EF) reached 16.3145×107. Finally, based on the excellent SERS property of h-BN/Ag/Ag2O 320℃ annealing composite, the SERS detection of food additive patent Blue V (PBV) was conducted in this paper. The results showed that the lowest detection concentration could reach 10-12 M, and the trace detection of synthetic dye PBV was realized. It has excellent spatial uniformity and anti-interference ability, which is of great significance in the actual scene detection of PBV. The h-BN/Ag/Ag2O 320 ℃ annealed composite constructed in this paper has both physical and chemical enhancement, and has significant advantages in ultra-low sensitive SERS detection of food additives.
{"title":"Research on the h-BN/Ag/Ag<sub>2</sub>O heterostructure was optimized by high temperature annealing and its surface-enhanced Raman scattering performance","authors":"None Zheng Lin-Qi, None Shi Shu-Hua, None Li Jin-Ze, None Wang Zi-Yu, None Li Shuang","doi":"10.7498/aps.72.20231105","DOIUrl":"https://doi.org/10.7498/aps.72.20231105","url":null,"abstract":"As a commonly used food additive, synthetic dyes are widely used in foods such as beverages, sweets and dairy products, and in the food processing process, excessive use of synthetic dyes may induce cell mutations, children's hyperactivity, genetic diseases and even cancer, posing a great threat to human health. As a fast, cheap, stable, ultra-sensitive and accurate detection method, SERS detection can reflect rich molecular fingerprint information through the vibration of the analyte, and accurately determine the trace amount of synthetic dyes in the actual environment. The metal/semiconductor heterostructure formed by the combination of plasmon metal and semiconductor is advantageous for the enhancement of photoinduced charge transfer efficiency (PICT), and has obvious advantages in the study of surface-enhanced Raman scattering. In this paper, the prepared hybrid substrate is annealed to further improve the surface-enhanced Raman scattering activity. Initially, high-density and monodisperse silver/silver oxide (Ag/Ag2O) nanoparticles were loaded onto two-dimensional hexagonal boron nitride (h-BN) nanosheets. On this basis, by annealing the system at high temperature, an efficient charge transfer channel is constructed, which greatly improves the PICT efficiency and chemical enhancement (CM). It was confirmed by experiments that the SERS signal intensity of h-BN/Ag/Ag2O material annealed at 320 ℃ with crystal violet (CV) as probe molecule was significantly increased by 18 times compared with unannealed material，enhancement factor (EF) reached 16.3145×107. Finally, based on the excellent SERS property of h-BN/Ag/Ag2O 320℃ annealing composite, the SERS detection of food additive patent Blue V (PBV) was conducted in this paper. The results showed that the lowest detection concentration could reach 10-12 M, and the trace detection of synthetic dye PBV was realized. It has excellent spatial uniformity and anti-interference ability, which is of great significance in the actual scene detection of PBV. The h-BN/Ag/Ag2O 320 ℃ annealed composite constructed in this paper has both physical and chemical enhancement, and has significant advantages in ultra-low sensitive SERS detection of food additives.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135400401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Lin Kaidong, None Lin Xiaoqian, None Lin Xubo
Monoclonal antibody inhibitors targeting PD1/PD-L1 immune checkpoints are gradually entering the market and have achieved certain positive effects in various types of tumor treatments. However, with the expansion of applications, the limitations of antibody drugs have gradually emerged, and small molecule compound inhibitors have become a new focus of attention for researchers. This study aims to use ligand-based and structure-based binding activity prediction methods to achieve virtual screening of small molecule compounds targeting PD-L1, thereby helping to accelerate the development of small molecule drugs. A dataset of PD-L1 small molecule inhibitory activity from relevant research literatures and patents was collected and machine learning activity judgment classification models with activity intensity prediction models were constructed based on different molecular characterization methods and algorithms. The two types of models filtered 68 candidate compounds with high PD-L1 inhibitory activity from a large drug-like small molecule screening pool. Ten of these compounds not only had good drug similarity and pharmacokinetics, but also showed the same level of binding strength and similar mechanism of action with previous hot compounds in molecule docking. This phenomenon was further verified in subsequent molecular dynamics simulation and binding free energy estimation. In this study, a virtual screening workflow integrating ligand-based method and structure-based method was developed, which effectively screened potential PD-L1 small molecule inhibitors in large compound databases, and is expected to help accelerate the application and expansion of tumor immunotherapy.
{"title":"Virtual screening of drugs targeting PD-L1 protein","authors":"None Lin Kaidong, None Lin Xiaoqian, None Lin Xubo","doi":"10.7498/aps.72.20231068","DOIUrl":"https://doi.org/10.7498/aps.72.20231068","url":null,"abstract":"Monoclonal antibody inhibitors targeting PD1/PD-L1 immune checkpoints are gradually entering the market and have achieved certain positive effects in various types of tumor treatments. However, with the expansion of applications, the limitations of antibody drugs have gradually emerged, and small molecule compound inhibitors have become a new focus of attention for researchers. This study aims to use ligand-based and structure-based binding activity prediction methods to achieve virtual screening of small molecule compounds targeting PD-L1, thereby helping to accelerate the development of small molecule drugs. A dataset of PD-L1 small molecule inhibitory activity from relevant research literatures and patents was collected and machine learning activity judgment classification models with activity intensity prediction models were constructed based on different molecular characterization methods and algorithms. The two types of models filtered 68 candidate compounds with high PD-L1 inhibitory activity from a large drug-like small molecule screening pool. Ten of these compounds not only had good drug similarity and pharmacokinetics, but also showed the same level of binding strength and similar mechanism of action with previous hot compounds in molecule docking. This phenomenon was further verified in subsequent molecular dynamics simulation and binding free energy estimation. In this study, a virtual screening workflow integrating ligand-based method and structure-based method was developed, which effectively screened potential PD-L1 small molecule inhibitors in large compound databases, and is expected to help accelerate the application and expansion of tumor immunotherapy.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135400403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The magnetic impurity effects and the existence of bound states (i.e. Yu-Shiba-Rusinov states) in superconductors have been a topic of great interest. Recently, the existence of Yu-Shiba-Rusinov states in graphene-based superconducting materials has been successfully observed in the laboratory. This paper establishes an effective Hamiltonian in real space to describe the superconducting state of graphene materials, considering a single magnetic impurity. It constructs the Bogoliubov-de Gennes (BdG) equation and performs self-consistency calculations on the superconducting order parameter. On this basis, the paper theoretically investigates the effects of magnetic impurities on graphene-like superconductors. The calculation results show that the Yu-Shiba-Rusinov state can only appear within the superconducting pairing symmetry of the traditional s-wave pairing. The position and strength of the bound state are related to the magnetic moment of the impurity, and it shows a notable electron-hole asymmetry. There are no bound states in the energy gap for other pairing symmetries. This theoretical calculation not only provides a reasonable explanation for experimental phenomena, but also demonstrates that the heterojunction system composed of graphene and traditional superconductors has an s-wave superconducting pairing induced by the proximity effect in the graphene layer.
{"title":"Single magnetic impurity effects in graphene based superconductors","authors":"None Zhao Zong-Yang, None Li Ming, None Zhou Tao","doi":"10.7498/aps.72.20230830","DOIUrl":"https://doi.org/10.7498/aps.72.20230830","url":null,"abstract":"The magnetic impurity effects and the existence of bound states (i.e. Yu-Shiba-Rusinov states) in superconductors have been a topic of great interest. Recently, the existence of Yu-Shiba-Rusinov states in graphene-based superconducting materials has been successfully observed in the laboratory. This paper establishes an effective Hamiltonian in real space to describe the superconducting state of graphene materials, considering a single magnetic impurity. It constructs the Bogoliubov-de Gennes (BdG) equation and performs self-consistency calculations on the superconducting order parameter. On this basis, the paper theoretically investigates the effects of magnetic impurities on graphene-like superconductors. The calculation results show that the Yu-Shiba-Rusinov state can only appear within the superconducting pairing symmetry of the traditional <i>s</i>-wave pairing. The position and strength of the bound state are related to the magnetic moment of the impurity, and it shows a notable electron-hole asymmetry. There are no bound states in the energy gap for other pairing symmetries. This theoretical calculation not only provides a reasonable explanation for experimental phenomena, but also demonstrates that the heterojunction system composed of graphene and traditional superconductors has an <i>s</i>-wave superconducting pairing induced by the proximity effect in the graphene layer.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135402164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Chen Chang, Shuai Sun, Long-Kun Du, Zhen-Wu Nie, Lin-Gui He, Yi Zhang, Peng Chen, Ke Bao, Wei-Tao Liu
Image, as a method of information acquisition, is indispensable for human beings, and it plays an irreplaceable role in military and civilian fields, such as detection and scouting, precision guidance, transportation, and industrial production. In the outdoor environment, the resolution, signal-to-noise ratio, and working distance of optical imaging are limited as result of the influence of background light, stray light, and atmospheric medium. In recent years, with the development of muti-discipline such as optics, physics, information theory, and computer science, the new optical imaging technologies continue to emerge, thus bringing new opportunities for outdoor optical imaging towards long-distance, large field of view and high information flux. As one of the new active imaging technologies, correlation imaging has the potential applications of robustness against turbulence and noise, and the possibility of beating the Rayleigh limit. It can deal with the problems better, such as sharp attenuation of optical power caused by long distances, detection of interference signals from environmental noise, and influence of turbulence. Based on the principle of optical imaging, this paper analyzes the factors affecting optical imaging, in terms of resolution, signal-to-noise ratio, spatial bandwidth product, and imaging distance under outdoor environment, focusing on the research progress of outdoor correlation imaging including imaging systems, signal-to-noise screening technology and imaging algorithm. In addition, we analyze the requirements of optical imaging for longer distances and broader field of view, and consider the fundamental problems and the key technologies.
{"title":"Research progress of correlation imaging under outdoor environment","authors":"Chen Chang, Shuai Sun, Long-Kun Du, Zhen-Wu Nie, Lin-Gui He, Yi Zhang, Peng Chen, Ke Bao, Wei-Tao Liu","doi":"10.7498/aps.72.20231245","DOIUrl":"https://doi.org/10.7498/aps.72.20231245","url":null,"abstract":"Image, as a method of information acquisition, is indispensable for human beings, and it plays an irreplaceable role in military and civilian fields, such as detection and scouting, precision guidance, transportation, and industrial production. In the outdoor environment, the resolution, signal-to-noise ratio, and working distance of optical imaging are limited as result of the influence of background light, stray light, and atmospheric medium. In recent years, with the development of muti-discipline such as optics, physics, information theory, and computer science, the new optical imaging technologies continue to emerge, thus bringing new opportunities for outdoor optical imaging towards long-distance, large field of view and high information flux. As one of the new active imaging technologies, correlation imaging has the potential applications of robustness against turbulence and noise, and the possibility of beating the Rayleigh limit. It can deal with the problems better, such as sharp attenuation of optical power caused by long distances, detection of interference signals from environmental noise, and influence of turbulence. Based on the principle of optical imaging, this paper analyzes the factors affecting optical imaging, in terms of resolution, signal-to-noise ratio, spatial bandwidth product, and imaging distance under outdoor environment, focusing on the research progress of outdoor correlation imaging including imaging systems, signal-to-noise screening technology and imaging algorithm. In addition, we analyze the requirements of optical imaging for longer distances and broader field of view, and consider the fundamental problems and the key technologies.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135501102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Tian Li-Man, None Wen Yong-Li, None Wang Yunfei, None Zhang Shanchao, None Li Jianfeng, None Du Jing-Song, None Yan Hui, None Zhu Shi-Liang
The propagator plays a central role in path integral theory and therefore has significant value in various modern quantum physics fields where path integral representations can be used. However, due to the fact that it has not been directly measured in experiments, progress in experimental studies of quantum systems based on path integral representations has been severely limited. Recently, we proposed a propagator measurement scheme based on direct measurement of the wave function and successfully performed the first experimental measurement of the propagator using a single photon experiment. Furthermore, in this study, the quantum principle of least action was demonstrated for the first time. This research successfully addressed the technical challenges of path integral experimental studies. In this article, we will review the research progress in this field, including a brief introduction to the basic concepts and research progress of direct wave function measurement, and a detailed description of the theoretical model, experimental design, and experimental results of propagator measurement. Finally, we will introduce an important application example, which is the experimental demonstration of the quantum principle of least action through propagator measurement. The research progress in propagator measurement reviewed in this article will provide important references for future experimental studies using this method.
{"title":"Research Progress of the Measurement of Propagators in Path Integrals","authors":"None Tian Li-Man, None Wen Yong-Li, None Wang Yunfei, None Zhang Shanchao, None Li Jianfeng, None Du Jing-Song, None Yan Hui, None Zhu Shi-Liang","doi":"10.7498/aps.72.20230902","DOIUrl":"https://doi.org/10.7498/aps.72.20230902","url":null,"abstract":"The propagator plays a central role in path integral theory and therefore has significant value in various modern quantum physics fields where path integral representations can be used. However, due to the fact that it has not been directly measured in experiments, progress in experimental studies of quantum systems based on path integral representations has been severely limited. Recently, we proposed a propagator measurement scheme based on direct measurement of the wave function and successfully performed the first experimental measurement of the propagator using a single photon experiment. Furthermore, in this study, the quantum principle of least action was demonstrated for the first time. This research successfully addressed the technical challenges of path integral experimental studies. In this article, we will review the research progress in this field, including a brief introduction to the basic concepts and research progress of direct wave function measurement, and a detailed description of the theoretical model, experimental design, and experimental results of propagator measurement. Finally, we will introduce an important application example, which is the experimental demonstration of the quantum principle of least action through propagator measurement. The research progress in propagator measurement reviewed in this article will provide important references for future experimental studies using this method.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202500","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Reducing the space charge effect and the time dispersion caused by the edge field effect of the scanning deflection system is the key to realize the 100-femtosecond streak tube. In this paper, a novel femtosecond streak tube is proposed and designed. The factors affecting the temporal resolution are analyzed theoretically and the specifications are given. Parameters including the electric field distribution and electron transmittance on the two common acceleration system structures (planar cathode -mesh accelerating electrode and planar cathode – slit accelerating electrode) are compared and analyzed theoretically. The results show that although the electric field distribution formed by the planar cathode – mesh accelerating electrode could form uniform electric field, the electron transmittance is very low; planar cathode-slit accelerating structure would defocus the photoelectron beam along the scanning direction, but the electron transmittance in the effective detection range of the cathode is as high as 100%. The defocusing of the photoelectron beam can be removed by setting a narrow slit in front of the anode. The focusing electrode adopts two groups of plate-like structures which are vertically placed front and back, forming one-dimensional focusing electric fields along the scanning and the slit direction, respectively. The spatial focusing electrode is placed close to the phosphor screen, which is beneficial to push back the cross-point of the electron beam along the spatial direction. Thus, the electron transit time dispersion in the condition of large electron density would decrease. At the same time, the anode can provide a post-accelerating voltage of +5000 V, which is beneficial to shorten the transit time and dispersion of the photoelectrons, thereby improving the temporal resolution. Based on the above theoretical analysis, a novel femtosecond streak tube is designed by using planar cathode-slit accelerating electrode, anisotropic focusing system and post-accelerating method. The influence of the anode slit width on the spatial and temporal resolution is simulated. The results show that the temporal resolution deteriorates with the increase of the anode slot width (10 μm ~ 50 μm), due to the increase of the anode slit width will lead to the gradual increase of the size of the electron spot along the scanning direction, which would lead to the increase of the technical time dispersion. In addition, this study gives the simulation results of the femtosecond streak tube when the anode slit width is in the range of 10~50 μm. The results show that the static spatial resolution is higher than 100 lp/mm @ MTF=10%, dynamic spatial resolution is higher than 29 lp/mm @ MTF = 10%, the temporal resolution is better than 122 fs in the range of 4 mm cathode effective detection length. When the effective detection length of the cathode is increased to 8 mm, the dynamic spatial resolution of the streak tube tube is higher than 22 lp/mm @ MTF=10%,
{"title":"100 fs time-resolved streak tube design based on anisotropy and post-acceleration technology","authors":"None Tian Li-Ping, None 陈萍, None Shen Ling-bin, None Chen Ping, None Liu Yu-zhu, None Chen Lin, None Hui Dan-dan, None Chen Xi-ru, None Zhao Wei, None Xue Yan-hua","doi":"10.7498/aps.73.20231382","DOIUrl":"https://doi.org/10.7498/aps.73.20231382","url":null,"abstract":"Reducing the space charge effect and the time dispersion caused by the edge field effect of the scanning deflection system is the key to realize the 100-femtosecond streak tube. In this paper, a novel femtosecond streak tube is proposed and designed. The factors affecting the temporal resolution are analyzed theoretically and the specifications are given. Parameters including the electric field distribution and electron transmittance on the two common acceleration system structures (planar cathode -mesh accelerating electrode and planar cathode – slit accelerating electrode) are compared and analyzed theoretically. The results show that although the electric field distribution formed by the planar cathode – mesh accelerating electrode could form uniform electric field, the electron transmittance is very low; planar cathode-slit accelerating structure would defocus the photoelectron beam along the scanning direction, but the electron transmittance in the effective detection range of the cathode is as high as 100%. The defocusing of the photoelectron beam can be removed by setting a narrow slit in front of the anode. The focusing electrode adopts two groups of plate-like structures which are vertically placed front and back, forming one-dimensional focusing electric fields along the scanning and the slit direction, respectively. The spatial focusing electrode is placed close to the phosphor screen, which is beneficial to push back the cross-point of the electron beam along the spatial direction. Thus, the electron transit time dispersion in the condition of large electron density would decrease. At the same time, the anode can provide a post-accelerating voltage of +5000 V, which is beneficial to shorten the transit time and dispersion of the photoelectrons, thereby improving the temporal resolution. Based on the above theoretical analysis, a novel femtosecond streak tube is designed by using planar cathode-slit accelerating electrode, anisotropic focusing system and post-accelerating method. The influence of the anode slit width on the spatial and temporal resolution is simulated. The results show that the temporal resolution deteriorates with the increase of the anode slot width (10 μm ~ 50 μm), due to the increase of the anode slit width will lead to the gradual increase of the size of the electron spot along the scanning direction, which would lead to the increase of the technical time dispersion. In addition, this study gives the simulation results of the femtosecond streak tube when the anode slit width is in the range of 10~50 μm. The results show that the static spatial resolution is higher than 100 lp/mm @ MTF=10%, dynamic spatial resolution is higher than 29 lp/mm @ MTF = 10%, the temporal resolution is better than 122 fs in the range of 4 mm cathode effective detection length. When the effective detection length of the cathode is increased to 8 mm, the dynamic spatial resolution of the streak tube tube is higher than 22 lp/mm @ MTF=10%, ","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202978","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
None Shi Peng-Fei, None Ma Xin-Ying, None Xiang Chuan, None Zhao Hong-Ge, None Li Yuan, None Gao Ren-Jing, None Liu Shu-Tian
For oblique incident electromagnetic waves, the generation of double reflection channels including retroreflection channel is of great significance to improve target recognition performance and navigation performance. In double channel reflection, controlling the proportion of retroreflection and specular reflection is the key to realize reflection power distribution. In order to realize the control of the proportion of the reflected power in each channel, a topology optimization method for designing the reflective metasurface microstructure with dual channel was proposed in this paper. The implementation mechanism and physical model of metasurface with dual reflection channel including retroreflection channel were constructed, and the topology optimization model of metasurface microstructure with specific power proportion of the retroreflection to specular reflection was established. As the numerical example, a dual channel metasurface reflector with a 1:1 ratio of retroreflection and specular reflection power was designed for a 10 GHz plane wave in the TE mode with -30 ° incident angle. The designed metasurface exhibited strong directionality in the retroreflective direction, and the reflection amplitude in both directions was similar. The retroreflective metasurface with the maximum retroreflection proportion was designed. The retroreflection proportion of the designed metasurface was 0.093. There was no specular reflection or other singular reflection, and the strong reflection on the metasurface was concentrated at -30 °. The ratio of the main beam power to the total reflection power was 0.900. The simulated and experimental results verified the feasibility of the proposed method.
{"title":"Topology optimization design of dual-channel metasurface structure with controllable amplitude of retroreflection and mirror reflection","authors":"None Shi Peng-Fei, None Ma Xin-Ying, None Xiang Chuan, None Zhao Hong-Ge, None Li Yuan, None Gao Ren-Jing, None Liu Shu-Tian","doi":"10.7498/aps.72.20230775","DOIUrl":"https://doi.org/10.7498/aps.72.20230775","url":null,"abstract":"For oblique incident electromagnetic waves, the generation of double reflection channels including retroreflection channel is of great significance to improve target recognition performance and navigation performance. In double channel reflection, controlling the proportion of retroreflection and specular reflection is the key to realize reflection power distribution. In order to realize the control of the proportion of the reflected power in each channel, a topology optimization method for designing the reflective metasurface microstructure with dual channel was proposed in this paper. The implementation mechanism and physical model of metasurface with dual reflection channel including retroreflection channel were constructed, and the topology optimization model of metasurface microstructure with specific power proportion of the retroreflection to specular reflection was established. As the numerical example, a dual channel metasurface reflector with a 1:1 ratio of retroreflection and specular reflection power was designed for a 10 GHz plane wave in the TE mode with -30 ° incident angle. The designed metasurface exhibited strong directionality in the retroreflective direction, and the reflection amplitude in both directions was similar. The retroreflective metasurface with the maximum retroreflection proportion was designed. The retroreflection proportion of the designed metasurface was 0.093. There was no specular reflection or other singular reflection, and the strong reflection on the metasurface was concentrated at -30 °. The ratio of the main beam power to the total reflection power was 0.900. The simulated and experimental results verified the feasibility of the proposed method.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136202979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
As a kind of quantum phenomenon, Hong-Ou-Mandel (HOM) interference is more robust against phase noise. Because of this feature, robust quantum holography emerges, through which wave function of interested photon can be retrieved according to HOM interference pattern. For better understanding and developing this method, we derive a theoretical framework of robust HOM holography. In the quantum holography scheme, test state and reference state interfere at beam splitter (BS). Then, degree of freedom (DOF) resolved detections (such as spatial resolved detection, temporal resolved detection or spectrum resolved detection) are used at the BS output ports, respectively. Based on the single photon detection results, the DOF resolved coincidence counts are postselected, producing interference patterns. The information of the test states is retrieved from the patterns. According to different test states and reference states, four combinations are analysed, including measuring the wave function of single photon state by using standard single photon state or coherent state and measuring the wave function of coherent state through using standard single photon state or coherent state. In all cases, information of the test states is reflected in normalized second-order correlation function or interference patterns in similar forms. Specially, the wave function of test states can be directly retrieved from the interference patterns, with no complex algorithm required. Besides, phase noise from environment has no influence on this kind quantum holography. Comparison between traditional holography and quantum holography is made and analysed.
{"title":"General Theory of quantum holography based on two-photon Interference","authors":"Yao-Kun Xu, Shi-Hai Sun, Yao-Yuan Zeng, Jun-Gang Yang, Wei-Dong Sheng, Wei-Tao Liu","doi":"10.7498/aps.72.20231242","DOIUrl":"https://doi.org/10.7498/aps.72.20231242","url":null,"abstract":"As a kind of quantum phenomenon, Hong-Ou-Mandel (HOM) interference is more robust against phase noise. Because of this feature, robust quantum holography emerges, through which wave function of interested photon can be retrieved according to HOM interference pattern. For better understanding and developing this method, we derive a theoretical framework of robust HOM holography. In the quantum holography scheme, test state and reference state interfere at beam splitter (BS). Then, degree of freedom (DOF) resolved detections (such as spatial resolved detection, temporal resolved detection or spectrum resolved detection) are used at the BS output ports, respectively. Based on the single photon detection results, the DOF resolved coincidence counts are postselected, producing interference patterns. The information of the test states is retrieved from the patterns. According to different test states and reference states, four combinations are analysed, including measuring the wave function of single photon state by using standard single photon state or coherent state and measuring the wave function of coherent state through using standard single photon state or coherent state. In all cases, information of the test states is reflected in normalized second-order correlation function or interference patterns in similar forms. Specially, the wave function of test states can be directly retrieved from the interference patterns, with no complex algorithm required. Besides, phase noise from environment has no influence on this kind quantum holography. Comparison between traditional holography and quantum holography is made and analysed.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134882412","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The exploration of electromagnetic field influences on material characteristics remains a pivotal concern within scientific investigations. Nonetheless, in the realm of computational condensed matter physics, traditional density functional theory's extrapolation to scenarios inclusive of external electromagentic fields poses considerable challenges. These issues largely stem from the disruption of translational symmetry by external fields inherent in periodic systems, rendering Bloch's theorem inoperative. Consequently, the employment of first-principles methodologies in calculating material properties in the presence of external fields becomes an intricate task, especially in circumstances where the external field cannot be approximated as a minor perturbation. Over the past two decades, a significant number of scholars within the field of computational condensed matter physics have dedicated their work towards the formulation and refinement of first-principles computational methodologies adept at handling periodic systems subjected to finite external fields. This paper endeavors to systematically recapitulate these theoretical methodologies and their application across a broad spectrum including, but not limited to, ferroelectric, piezoelectric, ferromagnetic, and multiferroic domains. In the initial segment of this paper, we provide a succinct exposition on modern theory of polarization and delineate the process of constructing two methodologies for computations in finite electric fields predicated on this theory in conjunction with density functional theory. The succeeding segment delves into the integration of external magnetic fields into density functional theory and examines the accompanying computational procedures alongside the challenges they present. In the third segment, we firstly reflect on the first-principles effective Hamiltonian method, prevalent in the study of magnetic, ferroelectric and multiferroic systems, along with its adaptations for situations involving external fields. Concluding the paper, we introduce the exciting developments in constructing effective Hamiltonian models using neural network methods from machine learning, and their extensions under consideration of external fields.
{"title":"First-principles Calculation Methods for Periodic Systems Under External Electromagnetic Fields","authors":"None Lv Chengye, None Chen Yingwei, None Xie Muting, None Li Xueyang, None Yu Hongyu, None Zhong Yang, None Xiang Hongjun","doi":"10.7498/aps.72.20231313","DOIUrl":"https://doi.org/10.7498/aps.72.20231313","url":null,"abstract":"The exploration of electromagnetic field influences on material characteristics remains a pivotal concern within scientific investigations. Nonetheless, in the realm of computational condensed matter physics, traditional density functional theory's extrapolation to scenarios inclusive of external electromagentic fields poses considerable challenges. These issues largely stem from the disruption of translational symmetry by external fields inherent in periodic systems, rendering Bloch's theorem inoperative. Consequently, the employment of first-principles methodologies in calculating material properties in the presence of external fields becomes an intricate task, especially in circumstances where the external field cannot be approximated as a minor perturbation. Over the past two decades, a significant number of scholars within the field of computational condensed matter physics have dedicated their work towards the formulation and refinement of first-principles computational methodologies adept at handling periodic systems subjected to finite external fields. This paper endeavors to systematically recapitulate these theoretical methodologies and their application across a broad spectrum including, but not limited to, ferroelectric, piezoelectric, ferromagnetic, and multiferroic domains. In the initial segment of this paper, we provide a succinct exposition on modern theory of polarization and delineate the process of constructing two methodologies for computations in finite electric fields predicated on this theory in conjunction with density functional theory. The succeeding segment delves into the integration of external magnetic fields into density functional theory and examines the accompanying computational procedures alongside the challenges they present. In the third segment, we firstly reflect on the first-principles effective Hamiltonian method, prevalent in the study of magnetic, ferroelectric and multiferroic systems, along with its adaptations for situations involving external fields. Concluding the paper, we introduce the exciting developments in constructing effective Hamiltonian models using neural network methods from machine learning, and their extensions under consideration of external fields.","PeriodicalId":10252,"journal":{"name":"Chinese Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135550697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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