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Entanglement of two jaynes-cummings atoms in single excitation space

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arXiv 2020年

作者： Yang, Ya Liu, Yan Lu, Jing Zhou, Lan Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Department of Physics Synergetic Innovation Center of Quantum Effects and Applications Key Laboratory for Matter Microstructure and Function of Hunan Province Hunan Normal University Changsha410081 China College of Physics and Electronic Engineering Hengyang Normal University Hengyang421002 China

We study the entanglement dynamics of two atoms coupled to their own Jaynes-Cummings cavities in single-excitation space. Here we use the concurrence to measure the atomic entanglement. And the partial Bell states as initial states are considered. Our analysis suggests that there exist collapses and recovers in the entanglement dynamics. The physical mechanism behind the entanglement dynamics is the periodical information and energy exchange between atoms and light fields. For the initial Partial Bell states, only if the ratio of two atom-cavity coupling strengths is a rational number, the evolutionary periodicity of the atomic entanglement can be found. And whether there is time translation between two kinds of initial partial Bell state cases depends on the odd-even number of the coupling strength ratio. Copyright © 2020, The Authors. All rights reserved.

关键词： Atoms

Ferroelectrically tunable topological phase transition in In2Se3 thin films

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Physical Review B 2024年第8期109卷 085432-085432页

作者： Zhiqiang Tian Ziming Zhu Jiang Zeng Chao-Fei Liu Yurong Yang Anlian Pan Mingxing Chen Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education School of Physics and Electronics Hunan Normal University Changsha 410081 China School of Physics and Electronics Hunan University Changsha 410082 People's Republic of China School of Science Jiangxi University of Science and Technology Ganzhou 341000 China National Laboratory of Solid State Microstructures and Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China Key Laboratory for Micro-Nano Physics and Technology of Hunan Province College of Materials Science and Engineering Hunan University Changsha 410082 China State Key Laboratory of Powder Metallurgy Central South University Changsha 410083 China

Materials with ferroelectrically switchable topological properties are of interest for both fundamental physics and practical applications. Using first-principles calculations, we find that stacking ferroelectric α−In2Se3 monolayers into a bilayer leads to polarization-dependent band structures, which yields polarization-dependent topological properties. Specifically, we find that the states with interlayer ferroelectric couplings are quantum spin Hall insulators, while those with antiferroelectric polarizations are normal insulators. We further find that In2Se3 trilayer and quadlayer exhibit nontrivial band topology as long as in the structure the ferroelectric In2Se3 bilayer is antiferroelectrically coupled to In2Se3 monolayers or other ferroelectric In2Se3 bilayer. Otherwise the system is topologically trivial. The reason is that near the Fermi level the band structure of the ferroelectric In2Se3 bilayer has to be maintained for the nontrivial band topology. This feature can be used to design nontrivial band topology for the thicker films by a proper combination of the interlayer polarization couplings. The topological properties can be ferroelectrically tunable using the dipole locking effect. Our study reveals switchable band topology in a family of natural ferroelectrics, which provide a platform for designing new functional devices.

关键词： Ferroelectricity Topological materials 2-dimensional systems First-principles calculations

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

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arXiv 2022年

作者： Liu, Cheng Huang, Jin-Feng Tian, Lin Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China School of Natural Sciences University of California MercedCA95343 United States

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. © 2022, CC BY.

关键词： Photons

Canonical interpretation of the newly observed JP = 1+ structure X(2085)

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arXiv 2024年

作者： Li, Tian-Ge Zhang, Sheng-Chao Wang, Guan-Ying Lü, Qi-Fang Joint Research Center for Theoretical Physics School of Physics and Electronics Henan University Kaifeng475004 China Department of Physics Hunan Normal University Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Changsha410081 China Key Laboratory for Matter Microstructure and Function of Hunan Province Hunan Normal University Changsha410081 China

Inspired by the newly observed X(2085) by the BESIII Collaboration, we study the strong decay behaviors of excited axialvector strange mesons within the quark pair creation model. Our results indicate that the K1(1793)/K1(1861) can be regarded as the same K1(2P) state, and the K1(1911) is assigned as the K1(2P′) state. Considering the mass, spin-parity, and decay behaviors, we interpret the newly observed X(2085) as the radially excited K1(3P) state, which mainly decays into the ρ(1450)K, ω(1420)K, πK∗(1410), ρK1(1270), and ρK∗(892) final states. Also, the width of K1(3P′) state is predicted to be about 300 MeV, which can be searched for by future experiments. We expect that present calculations can help us to better understand the nature of the X(2085) structure. Copyright © 2024, The Authors. All rights reserved.

关键词： Excited states

Dynamical emission of phonon pairs in optomechanical systems

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arXiv 2021年

作者： Zou, Fen Liao, Jie-Qiao Li, Yong Beijing Computational Science Research Center Beijing100193 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Hunan Normal University Changsha410081 China Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China

Multiphonon state plays an important role in quantum information processing and quantum metrology. Here we propose a scheme to realize dynamical emission of phonon pairs based on the technique of stimulated Raman adiabatic passage in a single cavity optomechanical system, where the optical cavity is driven by two Gaussian pulse lasers. By exploring quantum trajectories of the state populations and the average phonon number, we find that the dynamical phonon-pair emission can be realized under the appropriate parameter conditions and is tunable by controlling the time interval between the consecutive pulses of pump lasers. In particular, the numerical results for the standard and generalized second-order correlation functions of the mechanical mode show that the system can behave as an antibunched phonon-pair emitter. Our proposal can be extended to achieve an antibunched n-phonon emitter, which has potential applications for on-chip quantum communications. Copyright © 2021, The Authors. All rights reserved.

关键词： Phonons

Nonreciprocal transition between two nondegenerate energy levels

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Photonics Research 2021年第5期9卷 879-886页

作者： XUNWEI XU YANJUN ZHAO HUI WANG AIXI CHEN YU-XI LIU 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 Department of Applied Physics East China Jiaotong UniversityNanchang 330013China Key Laboratory of Opto-electronic Technology Ministry of EducationBeijing University of TechnologyBeijing 100124China Center for Emergent Matter Science(CEMS) RIKENWakoSaitama 351-0198Japan Department of Physics Zhejiang Sci-Tech UniversityHangzhou 310018China Institute of Microelectronics Tsinghua UniversityBeijing 100084China Frontier Science Center for Quantum Information Beijing 100084China

Stimulated emission and absorption are two fundamental processes of light–matter interaction, and the coefficients of the two processes should be equal. However, we will describe a generic method to realize the significant difference between the stimulated emission and absorption coefficients of two nondegenerate energy levels, which we refer to as a nonreciprocal transition. As a simple implementation, a cyclic three-level atom system, comprising two nondegenerate energy levels and one auxiliary energy level, is employed to show a nonreciprocal transition via a combination of synthetic magnetism and reservoir engineering. Moreover, a single-photon nonreciprocal transporter is proposed using two one-dimensional semi-infinite coupled-resonator waveguides connected by an atom with nonreciprocal transition effect. Our work opens up a route to design atom-mediated nonreciprocal devices in a wide range of physical systems.

关键词： transition. effect. reciprocal

Evolution of flat bands in MoSe2/WSe2 moiré lattices: A study combining machine learning and band unfolding methods

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arXiv 2024年

作者： Yang, Shengguo Chen, Jiaxin Liu, Chao-Fei Chen, Mingxing Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education School of Physics and Electronics Hunan Normal University Changsha410081 China School of Science Jiangxi University of Science and Technology Ganzhou341000 China State Key Laboratory of Powder Metallurgy Central South University Changsha410083 China

Moiré lattices have served as the ideal quantum simulation platform for exploring novel physics due to the flat electronic bands resulting from the long wavelength moiré potentials. However, the large sizes of this type of system challenge the first-principles methods for full calculations of their electronic structures, thus bringing difficulties in understanding the nature and evolution of the flat bands. In this study, we investigate the electronic structures of moiré patterns of MoSe2/WSe2 by combining ab initio and machine learning methods. We find that a flat band with a bandwidth of about 5 meV emerges below the valence band edge at the K point for the H-stacking at a twist angle of 3.89◦ without spin-orbit coupling effect. Then, it shifts dramatically as the twist angle decreases and becomes about 20 meV higher than the valence band maximum for the twist angle of 3.15◦. Multiple ultra-flat bands emerge as the twist angle is reduced to 1.7◦. The spin-orbit coupling leads to a giant spin splitting comparable to that observed in the untwisted system (about 0.45 eV) and is nearly independent of twisting and stacking. As a result, the K-valley flat band remains the valence band maximum with the inclusion of spin-orbit coupling. Band unfolding reveals that the ultra-flat bands formed by the Γ and K valleys show distinct behaviors. The Γ-valley flat bands are sensitive to the interlayer coupling, thus experiencing dramatic changes as the twist angle decreases. In contrast, the K-valley flat band, which shows a weak dependence on the interlayer coupling, is mainly modulated by structural reconstruction. Therefore, a relatively small angle (2.13◦) is required to generate the K-valley flat band, which experiences a transition from the honeycomb to the triangular lattice as the twist angle decreases. © 2024, CC BY.

关键词： Spin orbit coupling

Controllable generation of mechanical quadrature squeezing via dark-mode engineering in cavity optomechanics

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arXiv 2023年

作者： Huang, Jian Lai, Deng-Gao Liao, Jie-Qiao Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Theoretical Quantum Physics Laboratory RIKEN Cluster for Pioneering Research Saitama Wako-shi351-0198 Japan

Quantum squeezing is an important resource in modern quantum technologies, such as quantum precision measurement and continuous-variable quantum information processing. The generation of squeezed states of mechanical modes is a significant task in cavity optomechanics. Motivated by recent interest in multimode optomechanics, it becomes an interesting topic to create quadrature squeezing in multiple mechanical resonators. However, in the multiple-degenerate-mechanical-mode optomechanical systems, the dark-mode effect strongly suppresses the quantum effects in mechanical modes. Here we study the generation of mechanical squeezing in a two-mechanical-mode optomechanical system by breaking the dark-mode effect with the synthetic-gauge-field method. We find that when the mechanical modes work at a finite temperature, the mechanical squeezing is weak or even disappeared due to the dark-mode effect, while the strong mechanical squeezing can be generated once the dark-mode effect is broken. In particular, the thermal-phonon-occupation tolerance of the mechanical squeezing is approximately three orders of magnitude larger than that without breaking the dark-mode effect. We also generalize this method to break the dark modes and to create the mechanical squeezing in multiple-mechanical-mode optomechanical systems. Our results describe a general physical mechanism and pave the way towards the generation of noise-resistant quantum resources. Copyright © 2023, The Authors. All rights reserved.

关键词： Quantum optics

Thermal-noise-resistant optomechanical entanglement via general dark-mode control

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arXiv 2022年

作者： Huang, Jian Lai, Deng-Gao Liao, Jie-Qiao Key Laboratory of Low-Dimensional Quantum Structures Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Theoretical Quantum Physics Laboratory Riken Cluster for Pioneering Research Saitama Wako-shi351-0198 Japan

Quantum entanglement not only plays an important role in the study of the fundamentals of quantum theory, but also is considered as a crucial resource in quantum information science. The generation of macroscopic entanglement involving multiple optical and mechanical modes is a desired task in cavity optomechanics. However, the dark-mode effect is a critical obstacle against the generation of quantum entanglement in multimode optomechanical systems consisting of multiple degenerate or near-degenerate mechanical modes coupled to a common cavity mode. Here we propose an auxiliary-cavity-mode method to enhance optomechanical entanglement in a multimode optomechanical system by breaking the dark-mode effect. We find that the introduction of the auxiliary cavity mode not only assists the entanglement creation between the cavity mode and the mechanical modes, but also improves the immunity of the optomechanical entanglement to the thermal excitations by about three orders of magnitude. We also study the optomechanical entanglement in the network-coupled optomechanical system consisting of two mechanical modes and two cavity modes. By analyzing the correspondence between the optomechanical entanglement and the darkmode effect, we find that optomechanical entanglement can be largely enhanced once the dark mode is broken. In addition, we study the mechanical entanglement and find that it is negligibly small. We also present some discussions on the experimental implementation with a microwave optomechanical setup, on the relationship between the dark-mode-breaking mechanism and the center-of-mass and relative coordinates, and on the explanation of the important role of the dark-mode breaking in the enhancement of optomechanical entanglement. Our results pave the way towards the preparation of entangled optomechanical networks and noise-resistant quantum resources. Copyright © 2022, The Authors. All rights reserved.

关键词： Quantum entanglement