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Thermodynamic nature of black holes in coexistence region

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Science China(physics,Mechanics & Astronomy) 2024年第5期67卷 27-32页

作者： Shao-Wen Wei Yu-Xiao Liu Lanzhou Center for Theoretical physics Key Laboratory of Theoretical Physics of Gansu Provinceand Key Laboratory of Quantum Theory and Applications of Mo ELanzhou UniversityLanzhou 730000China Institute of Theoretical physics&Research Center of gravitation Lanzhou UniversityLanzhou 730000China

Studying the system state of coexistence regions will peek into to reveal microscopic interactions between different phases of a thermodynamic system.However,there is no effective method to study thermodynamic nature of the coexistence black hole regions for the failure of the equation of state.Aiming at these coexistence states,in this work,we develop a general approach by introducing two new ratio parameters.The first one is the ratio of the horizon radii of the saturated coexistence small and large black holes,and the second one measures that of the small black hole molecule number to the total molecule number.We demonstrate that the first parameter can serve as an order parameter to characterize the first-order phase transition.The study also shows that the black hole state in the coexistence region is uniquely determined by these two introduced parameters bounded between 0 and 1.These results are quite significant in the analytical study of phase transition and the microscopic nature of black hole in the coexistence regions.

关键词： transition. state. thermodynamic

Tunable quantum anomalous Hall effects in ferromagnetic van der Waals heterostructures

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National Science Review 2024年第3期11卷 100-107页

作者： Feng Xue Yusheng Hou Zhe Wang Zhiming Xu Ke He Ruqian Wu Yong Xu Wenhui Duan Beijing Academy of quantum Information Sciences State key laboratory of Low Dimensional quantum physics Department of Physics Tsinghua University Guangdong Provincial key laboratory of Magnetoelectric physics and Devices Center for Neutron Science and Technology School of Physics Sun Yat-sen University State key laboratory of Surface physics Key Laboratory of Computational Physical Sciences and Department of PhysicsFudan University Frontier Science Center for quantum Information Department of physics and Astronomy University of California-Irvine Tencent quantum laboratory Tencent Technology(Shenzhen)Co.Ltd RIKEN Center for Emergent Matter Science(CEMS) Institute for Advanced Study Tsinghua University

The quantum anomalous Hall effect（QAHE） has unique advantages in topotronic applications, but it is still challenging to realize the QAHE with tunable magnetic and topological properties for building functional devices. Through systematic first-principles calculations, we predict that the in-plane magnetization induced QAHE with Chern numbers C = ±1 and the out-of-plane magnetization induced QAHE with high Chern numbers C = ±3 can be realized in a single material candidate, which is composed of van der Waals（vdW）coupled Bi and MnBi2Te4monolayers. The switching between different phases of QAHE can be controlled in multiple ways, such as applying strain or（weak） magnetic field or twisting the vdW materials. The prediction of an experimentally available material system hosting robust, highly tunable QAHE will stimulate great research interest in the field. Our work opens a new avenue for the realization of tunable QAHE and provides a practical material platform for the development of topological electronics.

关键词： quantum anomalous Hall effect topological quantum phase transition van der Waals heterostructures tunable Chern number high Chern number

Layer Hall effect induced by hidden Berry curvature in antiferromagnetic insulators

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National Science Review 2024年第2期11卷 15-23页

作者： Rui Chen Hai-Peng Sun Mingqiang Gu Chun-Bo Hua Qihang Liu Hai-Zhou Lu X.C.Xie Shenzhen Institute for quantum Science and Engineering and Department of physics Southern University of Science and Technology(SUSTech) International quantum Academy Institute for Theoretical physics and Astrophysics University of Würzburg School of Electronic and Information Engineering Hubei University of Science and Technology Guangdong Provincial key laboratory of Computational Science and Material Design Southern University of Science and Technology Shenzhen key laboratory of quantum Science and Engineering International Center for quantum Materials School of PhysicsPeking University Collaborative Innovation Center of quantum Matter CAS Center for Excellence in Topological quantum Computation University of Chinese Academy of Sciences

The layer Hall effect describes electrons spontaneously deflected to opposite sides at different layers, which has been experimentally reported in the MnBi2Te4thin films under perpendicular electric fields. Here, we reveal a universal origin of the layer Hall effect in terms of the so-called hidden Berry curvature, as well as material design principles. Hence, it gives rise to zero Berry curvature in momentum space but non-zero layer-locked hidden Berry curvature in real space. We show that, compared to that of a trivial insulator, the layer Hall effect is significantly enhanced in antiferromagnetic topological insulators. Our universal picture provides a paradigm for revealing the hidden physics as a result of the interplay between the global and local symmetries, and can be generalized in various scenarios.

关键词： layerHall effect hidden Berry curvature antiferromagnetic insulator axion insulator, quantum transport

Energy flux and waveforms by coalescing spinless binary system in effective one-body theory

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Science China(physics,Mechanics & Astronomy) 2024年第6期67卷 58-68页

作者： Sheng Long Weike Deng Jiliang Jing Department of physics Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China Center for gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

We present a study on the energy radiation rate and waveforms of the gravitational wave generated by coalescing spinless binary systems up to the third post-Minkowskian approximation in the effective one-body theory.To derive an analytical expansion of the null tetrad components of the gravitational perturbed Weyl tensorΨ4in the effective spacetime,we utilize the method proposed by Sasaki et al.During this investigation,we discover more general integral formulas that provide a theoretical framework for computing the results in any order.Subsequently,we successfully compute the energy radiation rate and waveforms of the gravitational wave,which include the results of the Schwarzschild case and the correction terms resulting from the dimensionless parameters a2and a3in the effective metric.

关键词： post-Minkowskian approximation effective one-body theory gravitational waveform template

Non-adiabatic holonomic quantum operations in continuous variable systems

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Science China(physics,Mechanics & Astronomy) 2024年第6期67卷 12-19页

作者： Hao-Long Zhang Yi-Hao Kang Fan Wu Zhen-Biao Yang Shi-Biao Zheng Fujian key laboratory of quantum Information and quantum Optics College of Physics and Information EngineeringFuzhou UniversityFuzhou 350116China

quantum operations by utilizing the underlying geometric phases produced in physical systems are favoured due to their potential robustness.When a system in a non-degenerate eigenstate undergoes an adiabatically cyclic evolution dominated by its Hamiltonian,it will get a geometric phase,referred to as the Berry Phase.While a non-adiabatically cyclic evolution produces an Aharonov-Anandan geometric phase.The two types of Abelian geometric phases are extended to the non-Abelian cases,where the phase factors become matrix-valued and the transformations associated with different loops are non-commutable.Abelian and non-Abelian(holonomic)operations are prevalent in discrete variable systems,whose limited(say,two)energy levels,form the qubit.While their developments in continuous systems have also been investigated,mainly due to that,bosonic modes(in,such as,cat states)with large Hilbert spaces,provide potential advantages in fault-tolerant quantum computation.Here we propose a feasible scheme to realize non-adiabatic holonomic quantum logic operations in continuous variable systems with cat codes.We construct arbitrary single-qubit(two-qubit)gates with the combination of single-and two-photon drivings applied to a Kerr Parametric Oscillator(KPO)(the coupled KPOs).Our scheme relaxes the requirements of the previously proposed quantum geometric operation strategies in continuous variable systems,providing an effective way for quantum control.

关键词： cat qubit continuous variable systems non-Abelian

Kerr black hole shadows cast by extraordinary light rays with Weyl corrections

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Science China(physics,Mechanics & Astronomy) 2024年第5期67卷 18-26页

作者： Songbai Chen Jiliang Jing Department of physics Institute of Interdisciplinary StudiesKey Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of EducationSynergetic Innovation Center for Quantum Effects and ApplicationsHunan Normal UniversityChangsha 410081China Center for gravitation and Cosmology College of Physical Science and TechnologyYangzhou UniversityYangzhou 225009China

We investigate the equation of motion for photons with Weyl corrections in a Kerr black hole spacetime in a small coupling case.Our results show that Weyl corrections yield phenomena of birefringence.The light rays propagating in the spacetime are separated into the ordinary rays and the extraordinary rays,and the propagation of the latter depends on the corrections.We probe the effects of Weyl corrections on the Kerr black hole shadows casted by the extraordinary rays and find that such corrections result in a weak stretching or squeezing in the vertical direction for the black hole shadows.Finally,we also study the change of the length of the Near-Horizon Extremal Kerr line(NHEK line)with Weyl corrections.These features could help us to understand the electrodynamics with Weyl corrections from black hole shadows.

关键词： correction light stretching

Mobility edges and localization characteristics in one-dimensional quasiperiodic quantum walk

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Chinese physics B 2024年第6期33卷 156-160页

作者：崔鑫辉王慧敏李志坚 Institute of Theoretical physics State Key Laboratory of Quantum Optics and Quantum DevicesShanxi UniversityTaiyuan 030006China

We construct a one-dimensional quasiperiodic quantum walk to investigate the localization–delocalization transition.The inverse participation ratio and Lyapunov exponent are employed as two indexes to determine the mobility edge, a critical energy to distinguish the energy regions of extended and localized states. The analytical solution of mobility edge is obtained by the Lyapunov exponents in global theory, and the consistency of the two indexes is confirmed. We further study the dynamic characteristics of the quantum walk and show that the probabilities are localized to some specific lattice sites with time evolution. This phenomenon is explained by the effective potential of the Hamiltonian which corresponds to the phase in the coin operator of the quantum walk.

关键词： quantum walk mobility edges quasiperiodicity

Determination of molecular energies via variational-based quantum imaginary time evolution in a superconducting qubit system

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Science China(physics,Mechanics & Astronomy) 2024年第4期67卷 1-11页

作者： Zhiwen Zong Sainan Huai Tianqi Cai Wenyan Jin Ze Zhan Zhenxing Zhang Kunliang Bu Liyang Sui Ying Fei Yicong Zheng Shengyu Zhang Jianlan Wu Yi Yin Zhejiang Province key laboratory of quantum Technology and Device School of PhysicsZhejiang UniversityHangzhou 310027China Tencent quantum laboratory Shenzhen 518057China

As a valid tool for solving ground state problems,imaginary time evolution(ITE)is widely used in physical and chemical simulations.Different ITE-based algorithms in their quantum counterpart have recently been proposed and applied to some real systems.We experimentally realize the variational-based quantum imaginary time evolution(QITE)algorithm to simulate the ground state energy of hydrogen(H_2)and lithium hydride(Li H)molecules in a superconducting qubit system.The H_2 molecule is directly simulated using the 3-qubit circuit with unitary-coupled clusters(UCC)ansatz.We also combine QITE with the cluster mean-field(CMF)method to obtain an effective Hamiltonian.The Li H molecule is correspondingly simulated using the 3-qubit circuit with hardware-efficient ansatz.For comparison,the Li H molecule is also directly simulated using the 4-qubit circuit with UCC ansatz at the equilibrium point.All the experimental results show a convergence within 4 iterations,with high-fidelity ground state energy obtained.For a more complex system in the future,the CMF may allow further grouping of interactions to obtain an effective Hamiltonian,then the hybrid QITE algorithm can possibly simulate a relatively large-scale system with fewer qubits.

关键词： quantum computation quantum algorithm superconducting qubit

Progress on the antiferromagnetic topological insulator MnBi2Te4

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National Science Review 2024年第2期11卷 33-49页

作者： Shuai Li Tianyu Liu Chang Liu Yayu Wang Hai-Zhou Lu X.C.Xie Hefei National laboratory International Center for quantum Materials School of Physics Peking University Institute for Nanoelectronic Devices and quantum Computing Fudan University Department of physics Harbin Institute of Technology Shenzhen Institute for quantum Science and Engineering and Department of physics Southern University of Science and Technology(SUSTech) quantum Science Center of Guangdong-Hong Kong-Macao Greater Bay Area(Guangdong) Shenzhen key laboratory of quantum Science and Engineering International quantum Academy Beijing Academy of quantum Information Sciences Beijing key laboratory of Optoelectronic Functional Materials&Micro-Nano Devices Department of Physics Renmin University of China State key laboratory of Low Dimensional quantum physics Department of PhysicsTsinghua University Frontier Science Center for quantum Information

Topological materials, which feature robust surface and/or edge states, have now been a research focus in condensed maTher physics. They represent a new class of materials exhibiting nontrivial topological phases,and provide a platform for exploring exotic transport phenomena, such as the quantum anomalous Hall effect and the quantum spin Hall effect. Recently, magnetic topological materials have attracted considerable interests due to the possibility to study the interplay between topological and magnetic orders.In particular, the quantum anomalous Hall and axion insulator phases can be realized in topological insulators with magnetic order. MnBi2Te4, as the first intrinsic antiferromagnetic topological insulator discovered, allows the examination of existing theoretical predictions; it has been extensively studied, and many new discoveries have been made. Here we review the progress made on MnBi2Te4from both experimental and theoretical aspects. The bulk crystal and magnetic structures are surveyed first, followed by a review of theoretical calculations and experimental probes on the band structure and surface states, and a discussion of various exotic phases that can be realized in MnBi2Te4. The properties of MnBi2Te4thin films and the corresponding transport studies are then reviewed, with an emphasis on the edge state transport. Possible future research directions in this field are also discussed.

关键词： MnBi2Te4 magnetic topological insulator antiferromagnetic quantum anomalous Hall effect axion insulator