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Dark-state engineering in Fock-state lattices

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arXiv 2024年

作者： Zhao, Xuan Xu, Yi Kuang, Le-Man 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 Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

Fock-state lattices (FSLs) are becoming an emerging research hotspot in quantum physics, not only because the FSLs provide a new perspective for studying atom-field interactions, but also because they build the connection between quantum optics and condensed matter physics. Owing to the multiple transition paths in the lattices, inherent quantum interference effect exists in these systems, and hence how to find new quantum coherent phenomena and exploit their applications becomes a significant and desired task in this field. In this work, we study the dark-state effect in the FSLs generated by the multimode Jaynes-Cummings (JC) models. By considering the FSLs in certain-excitation-number subspaces, we study the dark states with respect to the states associated with the atomic excited state using the arrowhead-matrix method. We find that there exist dark-state subspaces with the dimensions determined by the number of orthogonal dark states. When the dimension is larger than one, the forms of these dark-state bases are not unique. Further, we obtain the number and form of the orthogonal dark states in the two-, three-, and four-mode JC models. In addition, we find that for a general N-mode JC model, there are CNN+−n2−2 orthogonal dark states in the n-excitation subspace. We also build the relationship between the dark modes and dark states. Our work will pave the way for exploring quantum optical effects and quantum information processing based on the FSLs. Copyright © 2024, The Authors. All rights reserved.

关键词： Jaynes-Cummings model

Chiral-cat-state generation via the Sagnac-Fizeau effect

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arXiv 2024年

作者： Liu, Yu-Hong Yin, Xian-Li Jing, Hui Kuang, Le-Man 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 Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

Chiral quantum state generation is an interesting topic in quantum physics and quantum information science. Here we propose an approach for generating chiral cat states in a spinning resonator supporting both the clockwise (CW) and counterclockwise (CCW) traveling modes, which are dispersively coupled to a two-level atom. The physical mechanism for the chiral-cat-state generation is based on the Sagnac-Fizeau effect. Concretely, when the resonator is rotating, the CW and CCW modes have different frequency detuning with respect to the atomic transition frequency and hence the atomic-state-dependent rotating angular velocities for the CW and CCW modes in phase space are different. This mode-dependent evolution leads to a chirality mechanism in the state generation. Based on the mode-dependent conditional rotation evolution and atomic projection measurement at proper time, we achieve the separate generation of cat states in the CW mode and coherent states in the CCW mode. We also investigate quantum coherence properties of the generated states by examining their Wigner functions. In addition, the influence of the system dissipations on the state generation in the open-system case is investigated. Our work will provide some insights into the development of chiral optical devices and nonreciprocal photonics. Copyright © 2024, The Authors. All rights reserved.

关键词： Atoms

Generation and storage of spin squeezing via learning-assisted optimal control

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Physical Review A 2021年第3期103卷 032601-032601页

作者： Qing-Shou Tan Mao Zhang Yu Chen Jie-Qiao Liao Jing Liu Key Laboratory of Hunan Province on Information Photonics and Freespace Optical Communication College of Physics and Electronics Hunan Institute of Science and Technology Yueyang 414000 China MOE Key Laboratory of Fundamental Physical Quantities Measurement Hubei Key Laboratory of Gravitation and Quantum Physics PGMF and School of Physics Huazhong University of Science and Technology Wuhan 430074 China Tencent Lightspeed and Quantum Studios Shenzhen 518000 China Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province and Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha 410081 China

The generation and storage of spin squeezing is an attractive topic in quantum metrology and the foundation of quantum mechanics. The major models to realize the spin squeezing are the one- and two-axis twisting models. Here, we consider a collective spin system coupled to a bosonic field, and show that proper constant-value controls in this model can simulate the dynamical behavior of these two models. More interestingly, a better performance of squeezing can be obtained when the control is time varying, which is generated via a reinforcement learning algorithm. However, this advantage becomes limited if the collective noise is involved. To deal with this, we propose a four-step strategy for the construction of a type of combined controls, which include both constant-value and time-varying controls, but performed at different time intervals. Compared to the full time-varying controls, the combined controls not only give a comparable minimum value of the squeezing parameter over time, but also provide a better lifetime and larger full amount of squeezing. Moreover, the amplitude form of a combined control is simpler and more stable than the full time-varying control. Therefore, our scheme is very promising to be applied in practice to improve the generation and storage performance of squeezing.

关键词： Machine learning Quantum control Quantum metrology

Scaling Enhancement of Photon Blockade in Output Fields

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arXiv 2024年

作者： Liu, Zhi-Hao Xu, Xun-Wei 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 Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

Photon blockade enhancement is an exciting and promising subject that has been well studied for photons in cavities. However, whether photon blockade can be enhanced in the output fields remains largely unexplored. We show that photon blockade can be greatly enhanced in the mixing output field of a nonlinear cavity and an auxiliary (linear) cavity, where no direct coupling between the nonlinear and auxiliary cavities is needed. We uncover a biquadratic scaling relation between the second-order correlation of the photons in the output field and intracavity nonlinear interaction strength, in contrast to a quadratic scaling relation for the photons in a nonlinear cavity. We identify that this scaling enhancement of photon blockade in the output field is induced by the destructive interference between two of the paths for two photons passing through the two cavities. We then extend the theory to the experimentally feasible Jaynes-Cummings model consisting of a two-level system strongly coupled to one of the two uncoupled cavities, and also predict a biquadratic scaling law in the mixing output field. Our proposed scheme is general and can be extended to enhance blockade in other bosonic systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Jaynes-Cummings model

Analytical results for the superflow of spin-orbit-coupled Bose-Einstein condensates in optical lattices

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Physical Review A 2021年第6期103卷 063324-063324页

作者： Xiaobing Luo Zhou Hu Zhao-Yun Zeng Yunrong Luo Baiyuan Yang Jinpeng Xiao Lei Li Ai-Xi Chen Department of Physics Zhejiang Sci-Tech University Hangzhou 310018 China School of Mathematics and Physics Jinggangshan University Ji'an 343009 China State Key Laboratory of Low-Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 China Department of Physics and Key Laboratory for Matter Microstructure and Function of Hunan Province and Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Hunan Normal University Changsha 410081 China

In this paper we show that for sufficiently strong atomic interactions, there exist analytical solutions of current-carrying nonlinear Bloch states at the Brillouin zone edge to the model of spin-orbit-coupled Bose-Einstein condensates (BECs) with symmetric spin interaction loaded into optical lattices. These simple but generic exact solutions provide an analytical demonstration of some intriguing properties which have neither an analog in the regular BEC lattice systems nor in the uniform spin-orbit-coupled BEC systems. It is an analytical example for understanding the superfluid and other related properties of the spin-orbit-coupled BEC lattice systems.

关键词： Bose-Einstein condensates Cold gases in optical lattices Spin-orbit coupling

Simultaneous ground-state cooling of two levitated nanoparticles by coherent scattering

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arXiv 2023年

作者： Xu, Yi Liu, Yu-Hong Liu, Cheng 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 Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

Simultaneous ground-state cooling of two levitated nanoparticles is a crucial prerequisite for investigation of macroscopic quantum effects such as quantum entanglement and quantum correlation involving translational motion of particles. Here we consider a coupled cavity-levitated-particle system and present a detailed derivation of its Hamiltonian. We find that the y-direction motions of the two particles are decoupled from the cavity field and both the x- and z-direction motions, and that the z-direction motions can be further decoupled from the cavity field and the x-direction motions by choosing proper locations of the particles. We study the simultaneous cooling of these mechanical modes in both the three-mode and five-mode cavity-levitated optomechanical models. It is found that there exists a dark-mode effect when the two tweezers have the same powers, which suppress the simultaneous ground-state cooling. Nevertheless, the simultaneous ground-state cooling of these modes can be realized by breaking the dark-mode effect under proper parameters. Our system provides a versatile platform to study quantum effects and applications in cavity-levitated optomechanical systems. Copyright © 2023, The Authors. All rights reserved.

关键词： Nanoparticles

Theoretical Design of a Multifunctional Two-Dimensional HfGeTe4-Based Optoelectronic Device Utilizing the Anisotropic Photogalvanic Effect

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Physical Review Applied 2023年第5期20卷 054025-054025页

作者： Degao Xu Jindou Ru Biao Cai Jianing Tan Kaike Yang Guowei Yang Gang Ouyang Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province School of Physics and Electronics Hunan Normal University Changsha 410081 China Hongzhiwei Technology (Shanghai) Co. Ltd. 1599 Xinjinqiao Road Pudong Shanghai 201206 China State Key Laboratory of Optoelectronic Materials and Technologies School of Materials Science and Engineering Sun Yat-sen (Zhongshan) University Guangzhou 510275 China

Achieving desirable multifunctional optoelectronic devices requires consideration of indexes such as photoelectrical response, polarization sensitivity, energy consumption, power conversion efficiency (PCE), and direction dependence. To satisfy these requirements, we propose an anisotropic HfGeTe4-based optoelectronic device driven by the anisotropic photogalvanic effect (PGE) for high-performance photodetection and solar harvesting. We find a robust anisotropic PGE photocurrent Jph (Jx = 5.12, and Jy = 0.07) is generated under the illumination of linearly polarized light due to the noncentrosymmetric nature of pristine HfGeTe4. Through appropriate mechanical bending and heterostructure assembled with a black phosphorus monolayer, the photocurrent and anisotropic ratio can be substantially enhanced by 8 times and 22.98%, respectively. Moreover, it exhibits a very high PCE of 20.19% and a large optical conductivity of about 13 × 103Ω−1cm−1. Our results show a fascinating functional coupling architecture that simultaneously implements high polarization-resolved photodetection and solar-energy harvesting in self-powered low-dimensional devices, suggesting an efficient avenue to achieve multifunctional integrated optoelectronic devices.

关键词： Photogalvanic effect Spin optoelectronics 2-dimensional systems Chalcogenides Monolayer films Photodetectors Photovoltaic absorbers Solar cells

Optimal quantum strategy for locating Unruh channels

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arXiv 2024年

作者： Liu, Qianqian Liu, Tonghua Wen, Cuihong Wang, Jieci Department of Physics Synergetic Innovation Center for Quantum Effects Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control Ministry of Education Key Laboratory for Matter Microstructure and Function of Hunan Province Hunan Normal University Changsha410081 China School of Physics and Optoelectronic Yangtze University Jingzhou434023 China

From the perspective of quantum information theory, the effect of Unruh radiation on a two-level accelerated detector can be modeled as a quantum channel. In this work, we employ the tools of channel-position finding to locate Unruh channels. The signal-idler and idler-free protocols are explored to determine the position of the target Unruh channel within a sequence of background channels. We derive the fidelity-based bounds for the ultimate error probability of each strategy and obtain the conditions where the signal-idler protocol is superior to the protocol involving idler-free states. It is found that the lower bound of the error probability for the signal-idler scheme exhibits clear advantages in all cases, while the idler-free scheme can only be implemented when the temperature of the two channels is very close and the number of initial states is insufficient. Interestingly, it is shown that the optimal detection protocol relies on the residual correlations shared between the emitted probe state and the retained idler modes. Copyright © 2024, The Authors. All rights reserved.

关键词： Quantum optics

Two-dimensional hourglass Weyl nodal loop in monolayer Pb(ClO2)2 and Sr(ClO2)2

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arXiv 2022年

作者： Kang, Xin-Yue Zhang, Chunmei Chen, Mingxing Li, Si School of Physics Northwest University Xi’an710127 China Shaanxi Key Laboratory for Theoretical Physics Frontiers Xi’an710127 China School of Physics and Electronics Hunan Normal University Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control Ministry of Education Changsha410081 China

The hourglass fermions in solid-state materials have been attracting significant interest recently. However, realistic two-dimensional (2D) materials with hourglass-shaped band structures are still very scarce. Here, through the first-principles calculations, we identify the monolayer Pb(ClO2)2 and Sr(ClO2)2 materials as the new realistic materials platform to realize 2D hourglass Weyl nodal loop. We show that these monolayer materials possess an hourglass Weyl nodal loop circling around the Γ point and Weyl nodal line on the Brillouin zone (BZ) boundary in the absence of spin-orbit coupling (SOC). Through the symmetry analysis, we demonstrate that the hourglass Weyl nodal loop and Weyl nodal line are protected by the nonsymmorphic symmetries, and are robust under the biaxial strains. When we include the SOC, a tiny gap will be opened in the hourglass nodal loop and nodal line, and the nodal line can be transformed into the spin-orbit Dirac points. Our results provide a new realistic material platform for studying the intriguing physics associated with the 2D hourglass Weyl nodal loop and spin-orbit Dirac points. © 2022, CC BY-NC-ND.

关键词： Chlorine compounds