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Quantum phase transition of the Jaynes-Cummings model

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 1-9页

作者： Cheng liu Jin-Feng Huang Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan ProvinceDepartment of Physics and Synergetic Innovation Center for Quantum Effects and ApplicationsInstitute of Interdisciplinary StudiesHunan Normal UniversityChangsha 410081China

Herein,we propose an experimentally feasible scheme to show the quantum phase transition of the Jaynes-Cummings(JC)model by modulating the transition frequency of a two-level system in a quantum Rabi model with strong coupling.By tuning the modulation frequency and amplitude,the ratio of the effective coupling strength of the rotating terms to the effective cavity(atomic transition)frequency can enter the deep-strong coupling regime,while the counter-rotating terms can be neglected.Thus,a deep-strong JC model is obtained.The ratio of the coupling strength to resonance frequencies in the deep-strong JC model is two orders of magnitude larger than the corresponding ratio in the original quantum Rabi model.Our scheme can be employed in atom-cavity resonance and off-resonance cases,and it is valid over a broad range.The nonzero average cavity photons of the ground state indicate the emergence of a quantum phase transition.Further,we demonstrate the dependence of the phase diagram on the atom-cavity detuning and modulation parameters.All the parameters used in our scheme are within the reach of current experimental technology.Our scheme provides a new mechanism for investigating the critical phenomena of finite-sized systems without requiring classical field limits,thereby opening a door for studying fundamental quantum phenomena occurring in the ultrastrong and even deep-strong coupling regimes.

关键词： Jaynes-Cummings model quantum phase transition frequency modulation

Government environmental control measures on CO_(2) emission during the 2014 Youth Olympic Games in Nanjing:Perspectives from a top-down approach

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Journal of Environmental Sciences 2022年第3期34卷 165-178页

作者： cheng Hu Cheng liu Ning Hu Jun Hong Xinyue Ai College of Biology and the Environment Joint Center for sustainable Forestry in Southern ChinaNanjing Forestry UniversityNanjing 210037China Yale-NUIST Center on Atmospheric Environment International Joint Laboratory on Climate and Environment Change(ILCEC)Nanjing University of InformationScience&TechnologyNanjing 210044China Jiangxi Province Key Laboratory of the Causes and Control of Atmospheric Pollution/School of Water Resources and Environmental Engineering East China University of TechnologyNanchang 330013China National Key Laboratory on Electromagnetic Environmental Effects and Electro-Optical Engineering Army Engineering UniversityNanjing 210022China

Strict air pollution control measures were conducted during the Youth Olympic Games(YOG)period at Nanjing city and surrounding areas in August 2014.This event provides a unique chance to evaluate the effect of government control measures on regional atmospheric pollution and greenhouse gas emissions.Many previous studies have observed significant reductions of atmospheric pollution species and improvement in air quality,while no study has quantified its synergism on anthropogenic CO_(2)emissions,which can be coreduced with air pollutants.To better understand to what extent these pollution control measures have reduced anthropogenic CO_(2)emissions,we conducted atmospheric CO_(2)measurements at the suburban site in Nanjing city from 1^(st) July to 30^(th) September 2014 and 1^(st) August to 31^(st) August 2015,obvious decrease in atmospheric CO_(2)was observed between YOG and the rest period.By coupling the a prioriemission inventory with atmospheric transport model,we applied the scale factor Bayesian inversion approach to derive the posteriori CO_(2)emissions in YOG period and regular period.Results indicate CO_(2)emissions from power industry decreased by 45%,and other categories also decreased by 16%for manufacturing combusting,and 37%for non-metallic mineral production.Monthly total anthropogenic CO_(2)emissions were 9.8(±3.6)×10^(9) kg/month CO_(2) for regular period and decreased to 6.2(±1.9)×10^(9) kg/month during the YOG period in Nanjing city,with a 36.7%reduction.When scaling up to whole Jiangsu Province,anthropogenic CO_(2)emissions were 7.1(±2.4)×10^(10) kg/month CO_(2)for regular period and decreased to 4.4(±1.2)×10^(10)kg/month CO_(2) during the YOG period,yielding a 38.0%reduction.

关键词： Carbon dioxide Reduction measures Anthropogenic emissions Bayesian inversion

Variability of PM_(2.5) and O_(3) concentrations and their driving forces over Chinese megacities during 2018-2020

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Journal of Environmental Sciences 2023年第2期124卷 1-10页

作者： Tianyi Xu chengxin Zhang Cheng liu Qihou Hu School of Environmental Science and Optoelectronic Technology University of Science and Technology of ChinaHefei 230026China Department of Precision Machinery and Precision Instrumentation University of Science and Technology of ChinaHefei 230026China Center for Excellence in Regional Atmospheric Environment Institute of Urban EnvironmentChinese Academy of SciencesXiamen 361021China Key Laboratory of Environmental Optics and Technology Anhui Institute of Optics and Fine MechanicsChinese Academy of SciencesHefei 230031China Key Laboratory of Precision Scientific Instrumentation of Anhui Higher Education Institutes University of Science and Technology of ChinaHefei 230026China

Recently,air pollution especially fine particulate matters(PM_(2.5))and ozone(O_(3))has become a severe issue in China.In this study,we first characterized the temporal trends of PM_(2.5) and O_(3) for Beijing,Guangzhou,Shanghai,andWuhan respectively during 2018-2020.The annual mean PM2.5 has decreased by 7.82%-33.92%,while O_(3) concentration showed insignificant variations by-6.77%-4.65%during 2018-2020.The generalized additive models(GAMs)were implemented to quantify the contribution of individual meteorological factors and their gas precursors on PM_(2.5) and O_(3).On a short-term perspective,GAMs modeling shows that the daily variability of PM_(2.5) concentration is largely related to the variation of precursor gases(R=0.67-0.90),while meteorological conditions mainly affect the daily variability of O_(3) concentration(R=0.65-0.80)during 2018-2020.The impact of COVID-19 lockdown on PM_(2.5) and O_(3) concentrations were also quantified by using GAMs.During the 2020 lockdown,PM_(2.5) decreased significantly for these megacities,yet the ozone concentration showed an increasing trend compared to 2019.The GAMs analysis indicated that the contribution of precursor gases to PM_(2.5) and O_(3) changes is 3-8 times higher than that of meteorological factors.In general,GAMsmodeling on air quality is helpful to the understanding and control of PM2.5 and O3 pollution in China.

关键词： Air pollution PM_(2.5)and O_(3)trends Meteorology COVID-19 lockdown

PDA-BPs integrated mussel-inspired multifunctional hydrogel coating on PPENK implants for anti-tumor therapy,antibacterial infection and bone regeneration

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Bioactive Materials 2023年第9期27卷 546-559页

作者： Yizheng Li chengde liu Xitong cheng Jinyan Wang Yue Pan Cheng liu Shouhai Zhang Xigao Jian State Key Laboratory of Fine Chemicals Frontier Science Center for Smart MaterialsSchool of Chemical EngineeringDalian University of TechnologyDalian116024China Department of Polymer Science and Engineering Dalian University of TechnologyDalian116024China State Key Laboratory of Fine Chemicals Department of Pharmaceutical SciencesSchool of Chemical EngineeringDalian University of TechnologyDalian116024China Liaoning Province Engineering Research Centre of High-Performance Resins Dalian116024China

Currently,many cancer patients with bone defects are still threatened by tumor recurrence,postoperative bacterial infection,and massive bone loss.Many methods have been studied to endow bone implants with biocompatibility,but it is difficult to find an implant material that can simultaneously solve the problems of anticancer,antibacterial and bone promotion.Here,a multifunctional gelatin methacrylate/dopamine methacrylate adhesive hydrogel coating containing 2D black phosphorus(BP)nanoparticle protected by polydopamine(pBP)is prepared by photocrosslinking to modify the surface of poly(aryl ether nitrile ketone)containing phthalazinone(PPENK)implant.The multifunctional hydrogel coating works in conjunction with pBP,which can deliver drug through photothermal mediation and kill bacteria through photodynamic therapy at the initial phase followed by promotion of osteointegration.In this design,photothermal effect of pBP control the release of doxorubicin hydrochloride loaded via electrostatic attraction.Meanwhile,pBP can generate reactive oxygen species(ROS)to eliminate bacterial infection under 808 nm laser.In the slow degradation process,pBP not only effectively consumes excess ROS and avoid apoptosis induced by ROS in normal cells,but also degrade into PO43􀀀to promote osteogenesis.In summary,nanocomposite hydrogel coatings provide a promising strategy for treatment of cancer patients with bone defects.

关键词： Poly(aryl ether nitrile ketone) Nanocomposite hydrogel coating Black phosphorus Antitumor and PDT antibacterial therapy Osteogenesis

Deterministic generation of multi-photon bundles in a quantum Rabi model

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Science China(Physics,Mechanics & Astronomy) 2023年第2期66卷 1-12页

作者： Cheng liu Jin-Feng Huang Lin Tian Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan ProvinceDepartment of Physics and Synergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China School of Natural Sciences University of CaliforniaMerced 95343USA

Multi-photon bundle states are crucial for a broad range of applications such as quantum metrology,quantum lithography,quantum communication,and quantum biology.Here we propose a scheme that generates multi-photon bundles via virtual excitations in a quantum Rabi model.Our approach utilizes a Ξ-type three-level atom,where the upper two levels are coupled to a cavity field to form a quantum Rabi model with ultrastrong coupling,and the transition between the lower two levels is driven by two sequences of Gaussian pulses.We show that the driving pulses induce deterministic emission of multiple photons from the eigenstates of the quantum Rabi model via the stimulated Raman adiabatic passage technique,and hence can create bundles of multiple photons on-demand in the cavity output field.We calculate the generalized second-order correlation functions of the output photons,which reveal that the emitted photons form antibunched multi-photon bundles.

关键词： field quantum bundles

Investigation of Antimony ions doping on crystal structure and enhanced microwave dielectric performance of MgTa_(2)O_(6)ceramics

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Journal of Materiomics 2023年第4期9卷 701-708页

作者： Liang Shi Kui liu Cheng liu Dainan Zhang Huaiwu Zhang School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu610054China State Key Laboratory of Electronic Thin Films and Integrated Devices University of Electronic Science and Technology of ChinaChengdu610054China

Dielectric ceramics are promising in large-scale commercial millimeter-wave communication technology,such as 5G and the upcoming 6G,thanks to their excellent frequency selection characteristics and environmental stability.In this work,various contents of SbeO bonds were introduced into the MgTa_(2)O_(6)lattice using the solid-phase reaction method to investigate the effects on the lattice and microwave dielectric properties.XRD confirms that Sb ions successfully occupy Ta sites in the lattice and cause lattice shrinkage and crystallinity deterioration,which leads to a slight decrease in the quality factor.Furthermore,DFT calculations reveal that the doping leads to electron-biased aggregation toward O atoms,causing higher SbeO ionicity,but also attenuates the degree of ionization of Ta and Mg ions,which makes the dielectric constant of the doped samples vary non-monotonically with gradient doping.Satisfactorily,Sb doping substantially enhanced the thermal stability of the ceramics,with TCF values reduced from 36×10^(-6)℃^(-1)to 15×10^(-6)℃^(-1).

关键词： MgTa_(2)O_(6)ceramics Dielectric Raman DFT calculation

Relationship between structure and properties of microwave dielectric ceramic Li_((1+x))2MgTi3O8 based on Li non-stoichiometry

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Journal of Materiomics 2023年第2期9卷 279-288页

作者： Kui liu Cheng liu Jie Li Lichuan Jin Huaiwu Zhang School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu610054China State Key Laboratory of Electronic Thin Film and Integrated Devices University of Electronic Science and Technology of ChinaChengdu610054China

Li(_(1+x))2MgTi3O8(0.0≤x≤0.10)ceramics with Li non-stoichiometric ratios were prepared by the solidstate reaction method to inhibit the volatilization of Li.The effects of the Li non-stoichiometric ratios on the sintering behavior,crystal structure,microscopic morphology,Raman vibrations,electron density,and dielectric properties of Li(_(1+x))2MgTi3O8 ceramics were systematically investigated.The Li(1+0.06)_(2)MgTi_(3)O_(8)ceramics demonstrate the best dielectric properties withεr=26.33,Q×f=69435 GHz(@6.87 GHz,54%improvement),tf=2.95×10^(-6)℃^(-1).For the non-intrinsic factors,the high relative density(97.15%)and larger grain size(16.78 mm)allow the dielectric properties to be improved.As for the intrinsic factors,a reasonable excess of Li improves the bond ionicity of the MgdO bond,the lattice energy of the TidO bond,and the electron cloud density,thus optimizing the dielectric properties.Raman spectroscopy leads to the same result from the point of view of lattice vibrations.At the same time,the distortion of the polyhedra is also improved,so that tf also approaches 0.The improved Li(1+0.06)2MgTi3O8 has potential applications in microwave communication technology.

关键词： Li(1+x)_(2)MgTi_(3)O_(8) Raman vibration First-principles P-V-L theory Microwave dielectric

From 1D Nanofibers to 3D Nanofibrous Aerogels: A Marvellous Evolution of Electrospun SiO_(2) Nanofibers for Emerging Applications

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Nano-Micro Letters 2022年第12期14卷 40-78页

作者： Cheng liu Sai Wang Ni Wang Jianyong Yu Yi-Tao liu Bin Ding Innovation Center for Textile Science and Technology College of TextilesDonghua UniversityShanghai 201620People’s Republic of China

One-dimensional(1D)SiO_(2) nanofibers(SNFs),one of the most popular inorganic nanomaterials,have aroused widespread attention because of their excellent chemical stability,as well as unique optical and thermal characteristics.Electrospinning is a straightforward and versatile method to prepare 1D SNFs with programmable structures,manageable dimensions,and modifiable properties,which hold great potential in many cutting-edge applications including aerospace,nanodevice,and energy.In this review,substantial advances in the structural design,controllable synthesis,and multifunctional applications of electrospun SNFs are highlighted.We begin with a brief introduction to the fundamental principles,available raw materials,and typical apparatus of electrospun SNFs.We then discuss the strategies for preparing SNFs with diverse structures in detail,especially stressing the newly emerging three-dimensional SiO_(2) nanofibrous aerogels.We continue with focus on major breakthroughs about brittleness-to-flexibility transition of SNFs and the means to achieve their mechanical reinforcement.In addition,we showcase recent applications enabled by electrospun SNFs,with particular emphasis on physical protection,health care and water treatment.In the end,we summarize this review and provide some perspectives on the future development direction of electrospun SNFs.

关键词： SiO_(2)nanofibers Nanofibrous aerogels Structural design Mechanical reinforcement Multifunctional applications

Optimal Resource Allocation and Feasible Hexagonal Topology for Cyber-Physical Systems

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系统科学与复杂性学报:英文版 2023年第4期36卷 1583-1608页

作者： liu Yifa cheng Long State Key Laboratory of Multimodal Artificial Intelligence Systems Institute of AutomationChinese Academy of SciencesBeijing 100190China School of Artificial Intelligence University of Chinese Academy of SciencesBeijing 100049China

Networked cyber-physical systems are facing serious security threats from malicious attacks.It is noted that the networked cyber-physical system should take defense measures into account at the beginning of its construction.From the conservative defensive perspective,this paper proposes a robust optimal defense resource allocation strategy to reduce the maximum possible losses of the networked cyber-physical system caused by potential attacks.Then,based on the robust optimal allocation strategy,it can be proved that the topology of the networked cyber-physical system has a great influence on the loss function.In order to further improve security,the effects of adding redundant connections are investigated.Furthermore,by taking geographical knowledge into account,a hexagonal construction scheme is proposed for providing a geographically-feasible and economically-viable solution for building networked cyber-physical systems,where the loss function has a cubic decay.

关键词： Cyber-physical system hexagonal city planning optimization resource allocation