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Nonlinear time-reversal interferometry with arbitrary quadratic collective-spin interaction

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Chinese Physics B 2024年第8期33卷 63-70页

作者：胡知遥李其贤张轩晨张贺宾黄龙刚刘永椿 State Key Laboratory of Low-Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China School of Physics Xi'an Jiaotong UniversityXi'an 710049China China Fire and Rescue Institute Beijing 102202China Frontier Science Center for Quantum Information Beijing 100084China

Atomic nonlinear interferometry has wide applications in quantum metrology and quantum information *** we propose a nonlinear time-reversal interferometry scheme with high robustness and metrological gain based on the spin squeezing generated by arbitrary quadratic collective-spin interaction,which could be described by the Lipkin–Meshkov–Glick(LMG)*** optimize the squeezing process,encoding process,and anti-squeezing process,finding that the two particular cases of the LMG model,one-axis twisting and two-axis twisting outperform in robustness and precision,***,we propose a Floquet driving method to realize equivalent time reverse in the atomic system,which leads to high performance in precision,robustness,and *** study sets a benchmark for achieving high precision and high robustness in atomic nonlinear interferometry.

关键词： time-reversal interferometry spin squeezing quantum metrology

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Macroscopic mechanical systems are entering the quantum world

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National Science Review 2015年第1期2卷 9-10页

作者： yong-chun liu Yun-Feng Xiao School of Physics Peking University Collaborative Innovation Center of Quantum Matter

In the classic Chinese novel Journey to the West,the Monkey King has a special power that enables him to be in two or more places ***,an amazing thing such as this could never happen in real ***,in the quantum world,where the motions of objects obey the rules of quantum mechanics,this could *** weird quantum rules usually only apply in the

关键词： In Macroscopic mechanical systems are entering the quantum world

On-chip topological nanophotonic devices

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Chip 2022年第4期1卷 1-21页

作者： Cui-Cui Lu Hong-Yi Yuan Hong-Yu Zhang Wen Zhao Nian-En Zhang Yan-Ji Zheng Sayed Elshahat yong-chun liu Key Laboratory of Advanced Optoelectronic Quantum Architecture and Mea-surements of Ministry of Education Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic SystemsSchool of PhysicsBeijing Institute of TechnologyBeijing 100081China State Key Laboratory of Low-Dimensional Quantum Physics Department of PhysicsFrontier Science Center for Quantum InformationTsinghua UniversityBeijing 100084China

On-chip topological nanophotonic devices,which take photons as in-formation carriers with topological protection during light propaga-tion,have great application potential in the next generation photonic *** topological photonic states enable the nanophotonic de-vices to be robust and stable,immune to scattering even with imper-fect *** development,opportunities and challenges of the on-chip topological nanophotonic devices have attracted great atten-tion of scholars,and desired to be *** this review,topologi-cal devices were introduced in the order of functionalities on an in-tegrated photonic chip,*** light source,topological light waveguiding,topological light division and selection,topological light manipulation and topological light ***,we gave out-looks for predicting and promoting the performances of on-chip topo-logical nanophotonic devices from the angles of non-Hermitian sys-tems,non-Abelian topology,metasurfaces,intelligent algorithms and multiple functional topological nanophotonic *** review provides rich knowledge about on-chip topological nanophotonic *** insights in this paper will spark inspiration and inspire new thinking for the realization of topological photonic chips.

关键词： Topological photonics Nanophotonic devices Photonic chip

Pb induced dislocation defects of PtCo systems: Strain-triggered oxygen reduction reaction for PEMFC

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Nano Research 2024年第4期17卷 2462-2472页

作者： chun Jin Qiheng Wang Jingjun liu Beijing Key Laboratory of Electrochemical Process and Technology for Materials Beijing 100029China Beijing University of Chemical Technology Beijing 100029China

Design and development of advanced electrocatalysts with high performance and low Pt consumption are crucial for reducing the kinetic energy barrier of the cathode oxygen reduction reaction(ORR)and improving the efficiency of proton exchange membrane fuel cells(PEMFC).In this study,we demonstrate a Pb-modulated PtCo system for efficient ORR,in which the inclusion of Pb in ternary alloys induces dislocation defects due to the significant difference in atomic ***-PtCoPb was confirmed to exhibit significantly higher ORR activity and stability in acidic *** practical PEMFC applications,it outperforms the corresponding commercial Pt/C with a mass activity of 0.58 A·mgPt^(-1),making it a promising alternative to state-of-the-art Pt-based *** combination of experimental results and density functional theory(DFT)calculations offers valuable atomic-level insights into the dislocation *** with a larger atomic radius is located in the lattice stretching region below the dislocation slip plane,forming a structure similar to a Cottrell atmosphere,which reduces the dislocation energy and puts the system in a lower energy *** Cottrell atmosphere pins the dislocation structure and stabilizes the ternary *** adjusting the amount of added Pb,a moderate level of dislocation density induces a tuned strain effect,thereby enhancing the electrocatalytic mechanism by optimizing the electronic structure of the alloy surface and the adsorption and desorption of oxygen *** work provides valuable insights into the design and development of lattice dislocation defect structures to trigger strain effects for improving ORR performance.

关键词： dislocation defect strain effect Pb-modulated oxygen reduction reaction

Effect of post rolling stress on phase transformation behavior of microalloyed dual phase steel

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Journal of Iron and Steel Research(International) 2024年第3期31卷 688-699页

作者： Wen-quan Sun Sheng-yi yong Tie-heng Yuan Ting-song Yang An-rui He Chao liu Rui-chun Guo National Engineering Research Center for Advanced Rolling and Intelligent Manufacturing University of Science and Technology BeijingBeijing 100083China

The slow phase transformation of microalloyed dual phase steel makes the nonuniform stress and temperature fields during the post rolling cooling process have a significant impact on the phase transformation *** the relatively slow phase transformation of DP780 steel within the microalloyed dual phase steel series,the influence of stress on the phase transformation behavior of DP780 steel was *** quantify the nonuniform thermal and stress conditions in the steel coil,a thermo-mechanical coupled finite element model of the hot-rolled strip cooling process was *** on the simulation data,DP780 steel was chosen as the research material,and Gleeble 3500 thermal simulation equipment was used for experimental *** thermal expansion curves were analyzed through regression to establish the dynamic model of DP780 steel phase transformation under ***,metallographic analysis was conducted to determine phase transformation type and grain size of DP780 *** results confirmed that the stress promotes the occurrence of semi-diffusion-type bainite ***,an appropriate level of stress facilitates the growth of bainitic grains,while the increased stress inhibits the growth of ferritic grains.

关键词： Microalloyed dual phase steel Stress Bainitic transformation Grain Finite element method

Relation Between the Eventual Continuity and the E-property for Markov-Feller Semigroups

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Acta Mathematicae Applicatae Sinica 2024年第1期40卷 1-16页

作者： yong liu Zi-yu liu LMAM School of Mathematical SciencePeking UniversityBeijing100871China

We investigate some relations between two kinds of semigroup regularities, namely the e-property and the eventual continuity, both of which contribute to the ergodicity for Markov processes on Polish *** precisely, we prove that for Markov-Feller semigroup in discrete time and stochastically continuous MarkovFeller semigroup in continuous time, if there exists an ergodic measure whose support has a nonempty interior,then the e-property is satisfied on the interior of the support. In particular, it implies that, restricted on the support of each ergodic measure, the e-property and the eventual continuity are equivalent for the discrete-time and the stochastically continuous continuous-time Markov-Feller semigroups.

关键词： Markov-Feller semigroup ergodicity e-property eventual continuity

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Optimal phase sensitivity of atomic Ramsey interferometers with coherent spin states

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Frontiers of physics 2011年第3期6卷 251-257页

作者： Guang-ri JIN yong-chun liu Li YOU Department of Physics Beijing Jiaotong University Beijing 100044 China Department of Physics Tsinghua University Beijing 100085 China

We present a detailed analysis of phase sensitivity for a nonlinear Ramsey interferometer, which utilize effective mean-field interaction of a two-component Bose-Einstein condensate in phase ac- cumulation. For large enough particle number N and small phase shift φ, analytical results of the Ramsey signal and the phase sensitivity are derived for a product coherent state θ, 0）. When collisional dephasing is absent, we confirm that the optimal sensitivity scales as 2/N3/2 for polar angle of the initial state θ = π/4 or 3π/4. The best-sensitivity phase satisfies different transcendental equations, depending upon the initial state and the observable being measured after the phase accumulation. In the presence of the collisional dephasing, we show that the N-3/2-scaling rule of the sensitivity maintains with spin operators jx and jy measurements. A slightly better sensitivity is attainable for optimal coherent state with θ = π/6 or 5π/6.

关键词： Ramsey interferometry phase estimation Bose-Einstein condensates phase decay,one-axis twisting model

Loss-induced nonreciprocity

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Light(Science & Applications) 2021年第2期10卷 256-263页

作者： Xinyao Huang Cuicui Lu Chao Liang Honggeng Tao yong-chun liu State Key Laboratory of Low-Dimensional Quantum Physics Department of PhysicsTsinghua UniversityBeijing 100084China Key Laboratory of Advanced Optoelectronic Quantum Architecture and Measurements of Ministry of Education Beijing Key Laboratory of Nanophotonics and Ultrafine Optoelectronic SystemsSchool of PhysicsBeijing Institute of TechnologyBeijing 100081China Collaborative Innovation Center of Light Manipulations and Applications Shandong Normal UniversityJinan 250358China Frontier Science Center for Quantum Information Beijing 100084China

Nonreciprocity is important in both optical information processing and topological photonics *** principles for realizing non reciprocity rely on magnetic fields,spatiotemporal modulation,or *** we propose a generic principle for generating nonreciprocity by taking advantage of energy loss,which is usually regarded as *** loss in a resonance mode induces a phase lag,which is independent of the energy transmission *** multichannel lossy resonance modes are combined,the resulting interference gives rise to nonreciprocity,with different coupling strengths for the forward and backward directions,and unidirectional energy *** study opens a new avenue for the design of nonreciprocal devices without stringent requirements.

关键词： backward generating directions

Mechanism and control of nonuniform phase transformation of microalloyed dual-phase steel during cooling process after hot rolling

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Journal of Iron and Steel Research(International) 2024年第2期31卷 428-441页

作者： Wen-quan Sun Sheng-yi yong Tie-heng Yuan Chao liu San-bao Zhou Rui-chun Guo Meng-xia Tang National Engineering Research Center for Advanced Rolling and Intelligent Manufacturing University of Science and Technology BeijingBeijing100083China Strip Production Plant Xichang Steel and Vanadium Corporation of Pangang GroupXichang615000SichuanChina

After cooling in the hot rolling process,the metallographic structure of microalloyed dual-phase steel is nonuniform along the rolling direction,while the thickness fluctuation of microalloyed dual-phase steel with a nonuniform metallographic structure will occur during cold *** mechanism of nonuniform phase transformation of microalloyed dual-phase steels was studied during the cooling process after hot rolling,and the nonuniform phase transformation of microalloyed dual-phase steel was regulated during the cooling process after hot rolling through process ***,the empirical equation of phase transformation temperature was measured by a dilatometer considering thermal ***,the phase field and temperature field of laminar cooling process were calculated to provide initial boundary conditions for the finite element *** that,the coupling finite element model of the temperature phase transformation of the strip steel in coiling transportation process was *** simulation results show that the different thermal contact conditions of the microalloyed dual-phase steel during coil transportation lead to uneven cooling of the coil,which leads to nonuniform transformation of the coil along the rolling *** addition,by prolonging the time interval from coiling to unloading,the phenomenon of nonuniform phase transformation of microalloyed dual-phase steel can be effectively *** simulation results are applied to industrial *** application results show that prolonging the time interval from coiling to unloading can effectively improve the nonuniform phase transformation of microalloyed dual-phase steel in the cooling process after hot rolling.

关键词： Microalloyed dual-phase steel Thickness fluctuation Cooling Heat conduction Nonuniform phase transition Finite element method