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Vertical ferroelectricity in van der Waals materials: Models and devices

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Applied Physics Letters 2023年第14期123卷

作者： Yuwen Zhang Chunfeng Cui Chaoyu He Tao Ouyang Jin Li Mingxing Chen Chao Tang Hunan Key Laboratory for Micro-Nano Energy Materials and Device and School of Physics and Optoelectronics Xiangtan University Xiangtan 411105 Hunan China 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

Ferroelectricity has a wide range of applications in functional electronics, and it is extremely important for the development of the next generation of information-storage technologies. However, it is difficult to achieve in practice due to its special symmetry requirements. In this Letter, based on van der Waals stacking, a generic model is proposed for realizing ferroelectric devices in which a freely movable center layer is packaged in two fixed and symmetrically stacked layers. In this model, a ferroelectric phase transition can be realized between two equivalent and eccentric ground stacking states with opposite polarizations. By means of first-principles calculations, taking stacked hexagonal boron nitride (h-BN/h-BN/h-BN) and h-BN/graphene/h-BN as feasible models, we carefully evaluated the magnitude of ferroelectricity. The corresponding polarizations were estimated as 1.83 and 1.35 pC/m, values that are comparable to those observed in sliding ferroelectricity. Devices using this tri-layer model of vertical ferroelectricity can be constructed using arbitrary van der Waals semiconducting materials, and these will usually have low switching barriers. It is highly likely that optimized material combinations with remarkable polarization will be discovered from the huge candidate set this provides for future information-storage applications.

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Noise-Tolerant Optomechanical Entanglement via Synthetic Magnetism

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arXiv 2022年

作者： Lai, Deng-Gao Liao, Jie-Qiao Miranowicz, Adam Nori, Franco 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 and 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 Institute of Spintronics and Quantum Information Faculty of Physics Adam Mickiewicz University Poznań61-614 Poland Physics Department The University of Michigan Ann ArborMI48109-1040 United States

Entanglement of light and multiple vibrations is a key resource for multi-channel quantum information processing and memory. However, entanglement generation is generally suppressed, or even fully destroyed, by the dark-mode (DM) effect induced by the coupling of multiple degenerate or near-degenerate vibrational modes to a common optical mode. Here we propose how to generate optomechanical entanglement via DM breaking induced by synthetic magnetism. We find that at nonzero temperature, light and vibrations are separable in the DM-unbreaking regime but entangled in the DM-breaking regime. Remarkably, the threshold thermal phonon number for preserving entanglement in our simulations has been observed to be up to three orders of magnitude stronger than that in the DM-unbreaking regime. The application of the DM-breaking mechanism to optomechanical networks can make noise-tolerant entanglement networks feasible. These results are quite general and can initiate advances in quantum resources with immunity against both dark modes and thermal noise. Copyright © 2022, The Authors. All rights reserved.

关键词： Magnetism

Giant-cavity-based quantum sensors with enhanced performance

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arXiv 2022年

作者： Zhu, Y.T. Wu, R.B. Peng, Z.H. Xue, Shibei Department of Automation Shanghai Jiao Tong University Shanghai200240 China Key Laboratory of System Control and Information Processing Ministry of Education of China Shanghai200240 China Shanghai Engineering Research Center of Intelligent Control and Management Shanghai200240 China Center for intelligent and networked systems Department of Automation Tsinghua University Beijing100084 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 Department of Physics Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China

Recent progresses have revealed that quantum systems with multiple position-dependent couplings, e.g., giant atoms, can exhibit some unconventional phenomena, such as non-exponential decay etc. However, their potential applications are still open questions. In this paper, we propose a giant-cavity-based quantum sensor for the first time, whose performance can be greatly enhanced compared to traditional cavity-based sensors. In our proposal, two cavities couple to a dissipative reservoir at multiple points while they couple to a gain reservoir in a single-point way. To detecting a unknown parameter using this sensor, a waveguide is coupled to one of the cavities where detecting fields can pass through for homodyne detection. We find that multiple position-dependent couplings can induce an inherent non-reciprocal coupling between the cavities, which can enhance the performance of sensors. Output noise in our scheme can be reduced to the shot noise level, which is about one order magnitude lower than the results in Ref. [Lau and Clerk (2018)]. Besides, the signal-to-noise ratio per photon is also enhanced by about one order of magnitude. These results show that the multiple-point-coupling structure is beneficial to nowadays quantum devices. Copyright © 2022, The Authors. All rights reserved.

关键词： Couplings

Deterministic generation of nonclassical mechanical states in cavity optomechanics via reinforcement learning

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Physical Review A 2025年第5期111卷 053517-053517页

作者： Yu-Hong Liu Qing-Shou Tan Le-Man Kuang Jie-Qiao Liao 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 and Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha Hunan 410081 China Hunan Research Center of the Basic Discipline for Quantum Effects and Quantum Technologies Hunan Normal University Changsha 410081 China Key Laboratory of Hunan Province on Information Photonics and Freespace Optical Communication College of Physics and Electronics Hunan Institute of Science and Technology Yueyang Hunan 414000 China Institute of Interdisciplinary Studies Hunan Normal University Changsha Hunan 410081 China

Nonclassical mechanical states, as vital quantum resources for exploring macroscopic quantum behavior, have wide applications in the study of the fundamental quantum mechanics and modern quantum technology. In this work, we propose a scheme for deterministically generating nonclassical mechanical states in cavity optomechanical systems. By working in the eigenrepresentation of the nonlinear optomechanical systems, we identify the carrier-wave resonance conditions and seek optimal driving pulses for state preparations. Concretely, we employ the reinforcement learning method to optimize the pulsed driving fields, effectively suppressing the undesired transitions induced by both the pulsed driving fields and dissipations. This approach enables the high-fidelity preparation of phononic Fock states and superposed Fock states in the single-resonator optomechanical systems, as well as two-mode entangled states in the two-resonator optomechanical systems. The statistical properties of the generated states are also examined. Our results create an opportunity for quantum state engineering in quantum optics and quantum information science via reinforcement learning.

关键词： Quantum optics

Spatial-nonlocality-induced non-Markovian electromagnetically induced transparency in a single giant atom

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Physical Review A 2022年第4期106卷 043710-043710页

作者： Y. T. Zhu S. Xue R. B. Wu W. L. Li Z. H. Peng M. Jiang Department of Automation Shanghai Jiao Tong University Shanghai 200240 People's Republic of China Key Laboratory of System Control and Information Processing Ministry of Education of China Shanghai 200240 People's Republic of China Shanghai Engineering Research Center of Intelligent Control and Management Shanghai 200240 People's Republic of China Center for Intelligent and Networked Systems Department of Automation Tsinghua University Beijing 100084 People's Republic of 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 Department of Physics and Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha 410081 People's Republic of China School of Electronics and Information Engineering Soochow University Suzhou 215006 People's Republic of China

The nonlocal waveguide coupling of giant atoms can bring up novel physics and applications. In this paper, we find unconventional electromagnetically induced transparency in giant atoms that has not been reported so far. We present a consistent theory for describing the unconventional EIT which includes a real-space scattering method and a time-delayed master equation. Our analysis shows this phenomenon is a full quantum effect led by a quantized interaction between the atom and the waveguide. Our theory shows that it can be observed when the time delay between two neighboring coupling points is comparable to the relaxation time of the atom. This phenomenon results from the inherent nonlocality of the giant atom, which physically forces propagating fields to be standing waves in space and the atom exhibiting retardations in time.

关键词： Quantum optics with artificial atoms Scattering theory Quantum master equation

Coherent control of spin tunneling in a spin-orbit coupled bosonic triple well

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arXiv 2021年

作者： Luo, Yuxin Yi, Jia Li, Wenjuan Xie, Xin Luo, Xiaobing Luo, Yunrong Key Laboratory for Matter Microstructure and Function of Hunan Province Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control Ministry of Education School of Physics and Electronics Hunan Normal University Changsha410081 China School of Management Hunan University of Information Technology Changsha410151 China Department of Physics Zhejiang Sci-Tech University Hangzhou310018 China Department of Physics Jinggangshan University Ji'an 343009 China

We study the coherent control of spin tunneling for a spin-orbit (SO) coupled boson held in a driven triple well. Under high-frequency approximation, we analytically obtain the quasienergies of the SO-coupled bosonic triple-well system and fine energy band structure is displayed. By adjusting the driving parameters, we reveal that the directed selective spin-flipping or spin-conserving tunneling of a SO-coupled boson occurs along different pathways and in different directions. The analytical results are numerically confirmed and perfect agreements are found. Further, a scheme of quantum spin switch with or without spin-flipping is presented. These results may be useful for quantum information processing and the design of spintronic devices. © 2021, CC BY.

关键词： Bosons

Control the qubit-qubit coupling in the superconducting circuit with double-resonator couplers

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arXiv 2023年

作者： Wang, Hui Zhao, Yan-Jun Sun, Hui-Chen Xu, Xun-Wei Li, Yong Zheng, Yarui Liu, Qiang Li, Rengang Shandong Inspur Intelligence Research Institute Co. Ltd. Jinan China Shandong Yunhai Guochuang Innovative Technology Co. Ltd Jinan China Key Laboratory of Opto-electronic Technology Ministry of Education Beijing University of Technology Beijing China Institute for Quantum Computing Department of Physics and Astronomy University of Waterloo WaterlooONN2L 3G1 Canada 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 Shandong Yunhai Guochuang Innovative Technology Co. Ltd China Co. Ltd. Shenzhen518048 China

We propose a theoretical scheme of using two-fixed frequency resonator couplers to tune the interaction between two Xmon qubits. The indirect interaction between two qubits induced by two resonators can cancel each other, so the direct qubit-qubit coupling is not essential for the switching off. So we can suppress the static ZZ coupling with the weak direct qubit-qubit coupling and even eliminate the static ZZ coupling through the destructive interferences of the double-path couplers. The cross-kerr resonance can induce additional poles for the static ZZ coupling which should be kept away during the two-qubit gates. The double-resonator couplers scheme could unfreeze some restrictions during the design of superconducting quantum chips and mitigate the static ZZ coupling, which might supply a promising platform for future superconducting quantum chip. © 2023, CC BY-NC-SA.

关键词： Qubits

Resource-efficient Direct Characterization of General Density Matrix

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arXiv 2023年

作者： Xu, Liang Zhou, Mingti Tao, Runxia Zhong, Zhipeng Wang, Ben Cao, Zhiyong Xia, Hongkuan Wang, Qianyi Zhan, Hao Zhang, Aonan Yu, Shang Xu, Nanyang Dong, Ying Ren, Changliang Zhang, Lijian College of Metrology and Measurement Engineering China Jiliang University Hangzhou310018 China National Laboratory of Solid State Microstructures Key Laboratory of Intelligent Optical Sensing and Manipulation College of Engineering and Applied Sciences Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210093 China Research Center for Quantum Sensing Zhejiang Lab Hangzhou310000 China School of Electronic Control Chang’an University Xi’an710064 China Quantum Optics and Laser Science Blackett Laboratory Imperial College London Prince Consort Rd LondonSW7 2AZ United Kingdom 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

Sequential weak measurements allow for the direct extraction of individual density-matrix elements, rather than relying on global reconstruction of the entire density matrix, which opens a new avenue for the characterization of quantum systems. Nevertheless, extending the sequential scheme to multi-qudit quantum systems is challenging due to the requirement of multiple coupling processes for each qudit and the lack of appropriate precision evaluation. To address these issues, we propose a resource-efficient scheme (RES) that directly characterizes the density matrix of general multi-qudit systems while optimizing measurements and establishing a feasible estimation analysis. In the RES, an efficient observable of the quantum system is constructed such that a single meter state coupled to each qudit is sufficient to extract the corresponding density-matrix element. An appropriate model based on the statistical distribution of errors is utilized to evaluate the precision and feasibility of the scheme. We have experimentally applied the RES to the direct characterization of general single-photon qutrit states and two-photon entangled states. The results show that the RES outperforms sequential schemes in terms of efficiency and precision in both weak- and strong-coupling scenarios. This work sheds new light on the practical characterization of large-scale quantum systems and the investigation of their non-classical properties. © 2023, CC BY.

关键词： Photons

Light meson emissions of the selected charmonium-like states within compact tetraquark configurations

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arXiv 2022年

作者： Li, Ning He, Hui-Zhen Liang, Wei Lü, Qi-Fang Chen, Dian-Yong Dong, Yu-Bing 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 School of Physics and Electronics Hunan Key Laboratory of Nanophotonics and Devices Central South University Changsha410083 China Ibaraki Osaka567-0047 Japan School of Physics Southeast University Nanjing210094 China Lanzhou Center for Theoretical Physics Lanzhou University Lanzhou730000 China Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China Cas Beijing100049 China School of Physical Sciences University of Chinese Academy of Sciences Beijing101408 China

We adopt the quark pair creation model to investigate the light meson emissions of several charmoniumlike states. The quark pair creation model is applied to the four-body systems, and we calculate the pion/kaon emissions of the X(4700), Zc(4430), Y(4230), Y(4360), Y(4390) and Y(4660) within the compact tetraquark assumptions. It is found that the pion/kaon decay widths for the X(4700) and Zc(4430) are relatively small, while the partial decay widths for the resonances Y(4230), Y(4360), Y(4390) and Y(4660) are significant. We expect that our exploration of these decay behaviors can provide useful information for future experimental searches and theoretical interpretations. Copyright © 2022, The Authors. All rights reserved.

关键词： Bosons