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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 *** 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

Different topological phase transitions in the Su–Schrieffer–Heeger model under different disorder structures

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Chinese physics B 2024年第9期33卷 217-221页

作者： Yan Gu Zhanpeng Lu Shanxi Vocational University of Engineering Science and Technology Jinzhong 030619China Institute of Theoretical physics and State Key Laboratory of quantum optics and quantum optics Devices Shanxi UniversityTaiyuan 030006China

We investigate the topological phase transition in the Su–Schrieffer–Heeger model with the long-range hopping and quasi-periodic *** numerically calculating the real-space winding number,we obtain topological phase diagrams for different disordered *** diagrams suggest that topological phase transitions are different by selecting the specific disordered *** quasi-periodic modulation is applied to intracell hopping,the resulting disorder induces topological Anderson insulator(TAI)phase with high winding number(W=2),but the topological states are destroyed as the disorder ***,when intercell hoppings are modulated quasi-periodically,both TAI phase and the process of destruction and restoration of topological zero modes can be induced by *** topological states remain robust even under strong disorder *** work demonstrates that disorder effects do not always disrupt topological states;rather,with a judicious selection of disordered structures,topological properties can be preserved.

关键词： topological insulator quasi-periodic modulation

A proposal for detecting weak electromagnetic waves around 2.6μm wavelength with Sr optical clock

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Chinese physics B 2024年第4期33卷 452-457页

作者：韩弱水王伟汪涛 Department of physics and Chongqing Key Laboratory for Strongly Coupled PhysicsChongqing UniversityChongqing 401331China Center of Modern physics Institute for Smart City of Chongqing University in LiyangLiyang 213300China State Key Laboratory of quantum optics and quantum optics Devices Shanxi UniversityTaiyuan 030006China

Infrared signal detection is widely used in many *** to the detection principle,however,the accuracy and range of detection are *** to the ultra stability of the^(87)Sr optical lattice clock,external infrared electromagnetic wave disturbances can be responded *** the ac Stark shift of the clock transition,we propose a new method to detect infrared *** to our calculations,the theoretical detection accuracy in the vicinity of its resonance band of 2.6μm can reach the order of 10-14W,while the minimum detectable signal of common detectors is on the order of 10^(-10)W.

关键词： infrared signal detection ^(87)Sr optical lattice clock ac Stark shift ultra stability

Experimental observation of spontaneous symmetry breaking in a quantum phase transition

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Science China(physics,Mechanics & Astronomy) 2024年第2期67卷 34-39页

作者： Wen Ning Ri-Hua Zheng Jia-Hao Lu Fan Wu Zhen-Biao Yang Shi-Biao Zheng Fujian Key Laboratory of quantum Information and quantum optics College of Physics and Information EngineeringFuzhou UniversityFuzhou 350108China Hefei National Laboratory Hefei 230088China

Spontaneous symmetry breaking(SSB)plays a central role in understanding a large variety of phenomena associated with phase transitions,such as superfluid and *** far,the transition from a symmetric vacuum to a macroscopically ordered phase has been substantially *** process bridging these two distinct phases is critical to understanding how a classical world emerges from a quantum phase transition,but so far remains unexplored in *** here report an experimental demonstration of such a process with a quantum Rabi model engineered with a superconducting *** move the system from the normal phase to the superradiant phase featuring two symmetry-breaking field components,one of which is observed to emerge as the classical *** results demonstrate that the environment-induced decoherence plays a critical role in the SSB.

关键词： quantum phase transition Rabi model spontaneous symmetry breaking superconducting circuit Schrodinger cat states

Optimal preparation of Bose and Fermi atomic gas mixtures of ^(87)Rb and ^(40)K in a crossed optical dipole trap

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Chinese physics B 2024年第6期33卷 356-361页

作者：丁培波单标赵宇航杨雅婧陈良超孟增明王鹏军黄良辉 State Key Laboratory of quantum optics and quantum optics Devices Institute of Opto-electronicsCollaborative Innovation Center of Extreme OpticsShanxi UniversityTaiyuan 030006China Hefei National Laboratory Hefei 230000China

We report on the optimal production of the Bose and Fermi mixtures with ^(87) Rb and ^(40)K in a crossed optical dipole trap(ODT).We measure the atomic number and lifetime of the mixtures in combination of the spin state |F=9/2,m_(F)=9/2> of^(40)K and |1,1>of ^(87) Rb in the ODT,which is larger and longer compared with the combination of the spin state |9/2,9/2> of^(40)K and 12,2) of ^(87)Rb in the *** observe the atomic numbers of ^(87)Rb and ^(40)K shown in each stage of the sympathetic cooling process while gradually reducing the depth of the optical *** optimizing the relative loading time of atomic mixtures in the MOT,we obtain the large atomic number of ^(40)K(~6 ×10^(6)) or the mixtures of atoms with an equal number(~1.6 × 10^(6)) at the end of evaporative cooling in the *** experimentally investigate the evaporative cooling in an enlarged volume of the ODT via adding a third laser beam to the crossed ODT and found that more atoms(8 × 10^(6)) and higher degeneracy(T/T_(F)=0.25) of Fermi gases are *** ultracold atomic gas mixtures pave the way to explore phenomena such as few-body collisions and the Bose-Fermi Hubbard model,as well as for creating ground-state molecules of ^(87)Rb^(40)K.

关键词： optical dipole trap Bose and Fermi gas mixtures atomic lifetime

Interplay between topology and localization on superconducting circuits

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Chinese physics B 2024年第6期33卷 240-246页

作者：关欣霍炳燕陈刚 Department of Materials and Chemical Engineering Taiyuan UniversityTaiyuan 030032China State Key Laboratory of quantum optics and quantum optics Devices Institute of Laser SpectroscopyShanxi UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme optics Shanxi UniversityTaiyuan 030006China School of physics Zhengzhou UniversityZhengzhou 450001China

Topological insulators occupy a prominent position in the realm of condensed matter physics. Nevertheless, the presence of strong disorder has the potential to disrupt the integrity of topological states, leading to the localization of all *** study delves into the intricate interplay between topology and localization within the one-dimensional Su–Schrieffer–Heeger(SSH) model, which incorporates controllable off-diagonal quasi-periodic modulations on superconducting *** the application of external alternating current(ac) magnetic fluxes, each transmon undergoes controlled driving,enabling independent tuning of all coupling strengths. Within a framework of this model, we construct comprehensive phase diagrams delineating regions characterized by extended topologically nontrivial states, critical localization, and coexisting topological and critical localization phases. The paper also addresses the dynamics of qubit excitations, elucidating distinct quantum state transfers resulting from the intricate interplay between topology and localization. Additionally, we propose a method for detecting diverse quantum phases utilizing existing experimental setups.

关键词： topology localization superconducting circuits

Efficient loading of cesium atoms in a magnetic levitated dimple trap

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Chinese physics B 2024年第2期33卷 324-328页

作者：张国庆冯国胜李玉清武寄洲马杰 State Key Laboratory of quantum optics and quantum optics Devices Institute of Laser SpectroscopyCollege of Physics and Electronics EngineeringShanxi UniversityTaiyuan 030006China Department of Magnetic Resonance Imaging The First Hospital of Shanxi Medical UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme optics Shanxi UniversityTaiyuan 030006China

We report a detailed study of magnetically levitated loading of ultracold ^(133)Cs atoms in a dimple *** atomic sample was produced in a combined red-detuned optical dipole trap and dimple trap formed by two small waist beams crossing a horizontal *** magnetic levitation for the ^(133)Cs atoms forms an effective potential for a large number of atoms in a high spatial *** of the number of atoms loaded and trapped in the dimple trap on the magnetic field gradient and bias field is in good agreement with the theoretical *** method has been widely used to obtain the Bose–Einstein condensation atoms for many atomic species.

关键词： ultracold atom magnetic levitation dimple trap

Superradiance of ultracold cesium Rydberg |65D_(5/2)> → |66P_(3/2)>

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Chinese physics B 2024年第5期33卷 425-428页

作者：郝丽萍韩小萱白素英游秀芬焦月春赵建明 Department of Materials and Chemical Engineering Taiyuan UniversityTaiyuan 030032China Department of physics Taiyuan Normal UniversityJinzhong 030619China School of physics and Information Engineering Shanxi Normal UniversityTaiyuan 030031China State Key Laboratory of quantum optics and quantum optics Devices Institute of Laser SpectroscopyShanxi UniversityTaiyuan 030006China Collaborative Innovation Center of Extreme optics Shanxi UniversityTaiyuan 030006China

We investigate Rydberg |65D_(5/2)> → |66P_(3/2)> superradiance in dense ultracold cesium atoms,where the ground atoms are excited to |65D_(5/2)> Rydberg states via two-photon excitation in a standard magneto-optical *** superradiant spectrum of |65D_(5/2)> → |66P_(3/2)> is obtained using the state-selective field ionization *** observe its dynamic evolution process by varying the delay time of ionization field *** results show that the evolution process of |65D_(5/2)> →|66P_(3/2)> is much shorter than its radiation lifetime at room temperature,which verifies the superradiance *** dependence of the superradiance process on Rydberg atoms number N_(e) and principal quantum number n is *** results show that the superradiance becomes faster with increasing N_(e),while it is suppressed for stronger van der Waals(vdW) *** has potential applications in quantum technologies,and the Rydberg atom is an ideal medium for *** system is effective for studying the strong two-body interaction between Rydberg atoms.

关键词： Rydberg atom superradiance van der Waals interaction

quantum nonlocality evolution for two entangled mesoscopic fields under decoherence

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Communications in Theoretical physics 2024年第1期76卷 24-28页

作者： Zhao-Song Tan Shou-Bang Yang Zhen-Biao Yang Shi-Biao Zheng Fujian Key Laboratory of quantum Information and quantum optics Fuzhou UniversityFuzhouFujian 350116China

Investigation of the nonlocality evolution of entangled mesoscopic fields under decoherence not only is important for understanding the quantum–classical transition,but also has relevance to quantum communication and quantum computation protocols based on continuous *** to previous formulations of Bell inequalities,the system loses nonlocal features far before the disappearance of *** here construct a new version of Bell signal based on rotated and displaced on–off correlations,with which the Bell inequality is violated as long as there remains entanglement and the field state components keep ***,the nonlocal character revealed by our formulation decays much slower compared with those based on previous *** importantly,there exists a wide regime where the Bell inequality is restored with previous formulations but remains to be violated based on our correlation operators.

关键词： entangled mesoscopic fields rotated and displaced on-off correlations Bell inequality nonlocality evolution