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Domino cooling of a coupled mechanical-resonator chain via cold-damping feedback

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arXiv 2020年

作者： Lai, Deng-Gao Huang, Jian Hou, Bang-Pin Nori, Franco 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 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 College of Physics and Electronic Engineering Institute of Solid State Physics Sichuan Normal University Chengdu610068 China Physics Department The University of Michigan Ann ArborMI48109-1040 United States

We propose a domino-cooling method to realize simultaneous ground-state cooling of a coupled mechanicalresonator chain through an optomechanical cavity working in the unresolved-sideband regime. This dominoeffect cooling is realized by combining the cold-damping feedback on the first mechanical resonator with nearest-neighbor couplings between other neighboring mechanical resonators. We obtain analytical results for the effective susceptibilities, noise spectra, final mean phonon numbers, and cooling rates of these mechanical resonators, and find the optimal-cooling condition for these resonators. Particularly, we analyze a twomechanical-resonator case and find that by appropriately engineering either the laser power or the feedback, a flexible switch between symmetric and asymmetric ground-state cooling can be achieved. This could be used for preparing symmetric quantum states in mechanical systems. We also simulate the cooling performance of a coupled N-mechanical-resonator chain and confirm that these resonators can be simultaneously cooled to their quantum ground states in the unresolved-sideband regime. Under proper parameter conditions, the cooling of the mechanical-resonator chain shows a temperature gradient along the chain. This study opens a route to quantum manipulation of multiple mechanical resonators in the bad-cavity regime. © 2020, CC BY.

关键词： Resonators

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

Polarity induced electronic and atomic reconstruction at NdNiO2/SrTiO3 interfaces

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arXiv 2020年

作者： He, Ri Jiang, Peiheng Lu, Yi Song, Yidao Chen, Mingxing Jin, Mingliang Shui, Lingling Zhong, Zhicheng School of Information and Optoelectronic Science and Engineering South China Normal University Guangzhou510006 China Key Laboratory of Magnetic Materials Devices & Zhejiang Province Key Laboratory of Magnetic Materials and Application Technology Ningbo Institute of Materials Technology and Engineering Chinese Academy of Sciences Ningbo315201 China Institute for Theoretical Physics University of Heidelberg Heidelberg69120 Germany 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 of Ministry of Education Changsha410081 China International Academy of Optoelectronics at Zhaoqing South China Normal University Zhaoqing526238 China China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing100049 China

Superconductivity has recently been observed in Sr-doped NdNiO2 films grown on SrTiO3. Whether it is caused by or related to the interface remains an open question. To address this issue, we use density functional theory calculation and charge transfer self-consistent model to study the effects of polar discontinuity on the electronic and atomic reconstruction at the NdNiO2/SrTiO3 interface. We find that sharp interface with pure electronic reconstruction only is energetically unfavorable, and atomic reconstruction is unavoidable. We further propose a possible interface configuration that contain residual apical oxygen. These oxygen atoms lead to hybrids of dz2 and dx2-y2 states at the Fermi level, which weaken the single-band feature and may be detrimental to superconductivity. Copyright © 2020, The Authors. All rights reserved.

关键词： Nickel compounds

Resource-Efficient Direct Characterization of General Density Matrix

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Physical Review Letters 2024年第3期132卷 030201-030201页

作者： Liang Xu Mingti Zhou Runxia Tao Zhipeng Zhong Ben Wang Zhiyong Cao Hongkuan Xia Qianyi Wang Hao Zhan Aonan Zhang Shang Yu Nanyang Xu Ying Dong Changliang Ren Lijian Zhang College of Metrology & Measurement Engineering China Jiliang University Hangzhou 310018 China National Laboratory of Solid State Microstructures Key Laboratory of Intelligent Optical Sensing and Manipulation College of Engineering and Applied Sciences and Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing 210093 China Research Center for Quantum Sensing Zhejiang Lab Hangzhou 310000 China School of Electronic Control Chang’an University Xi’an 710064 China Quantum Optics and Laser Science Blackett Laboratory Imperial College London Prince Consort Road London SW7 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 and Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha 410081 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 multiqudit 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 multiqudit 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 Letter sheds new light on the practical characterization of large-scale quantum systems and the investigation of their nonclassical properties.

关键词： Optical quantum information processing Quantum foundations Quantum measurements Quantum tomography Weak values & weak measurements Weak measurements

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

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

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Physical Review A 2024年第1期109卷 012601-012601页

作者： Hui Wang Yan-Jun Zhao Hui-Chen Sun Xun-Wei Xu Yong Li Yarui Zheng Qiang Liu Rengang Li Shandong Inspur Intelligence Research Institute Co. Ltd. Jinan 250100 China Shandong Yunhai Guochuang Innovative Technology Co. Ltd. Jinan 250101 China Key Laboratory of Opto-electronic Technology Ministry of Education Beijing University of Technology Beijing 100124 China Institute for Quantum Computing and Department of Physics and Astronomy University of Waterloo Waterloo Ontario N2L 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 and Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha 410081 China Quantum Element Technology (Shen Zhen) Co. Ltd. Shenzhen 518048 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 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 chips.

关键词： Quantum computation Quantum control

Optimal control of linear Gaussian quantum systems via quantum learning control

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arXiv 2024年

作者： Liu, Yu-Hong Zeng, Yexiong Tan, Qing-Shou Dong, Daoyi Nori, Franco 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 Cluster for Pioneering Research RIKEN Wakoshi Saitama351-0198 Japan Quantum Computing Center RIKEN Wakoshi Saitama351-0198 Japan Key Laboratory of Hunan Province on Information Photonics and Freespace Optical Communication College of Physics and Electronics Hunan Institute of Science and Technology Yueyang414000 China School of Engineering and Information Technology University of New South Wales CanberraACT2600 Australia Department of Physics The University of Michigan Ann ArborMI48109-1040 United States Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

Efficiently controlling linear Gaussian quantum (LGQ) systems is a significant task in both the study of fundamental quantum theory and the development of modern quantum technology. Here, we propose a general quantum-learning-control method for optimally controlling LGQ systems based on the gradient-descent algorithm. Our approach flexibly designs the loss function for diverse tasks by utilizing first- and second-order moments that completely describe the quantum state of LGQ systems. We demonstrate both deep optomechanical cooling and large optomechanical entanglement using this approach. Our approach enables the fast and deep ground-state cooling of a mechanical resonator within a short time, surpassing the limitations of sideband cooling in the continuous-wave driven strong-coupling regime. Furthermore, optomechanical entanglement could be generated remarkably fast and surpass several times the corresponding steady-state entanglement, even when the thermal phonon occupation reaches one hundred. This work will not only broaden the application of quantum learning control, but also open an avenue for optimal control of LGQ systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Cooling

Cosmological constraints from type-I radio-loud quasars

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Physical Review D 2024年第4期109卷 043529-043529页

作者： L. Huang Z. Y. Tu N. Chang F. F. Song F. He X. Y. Fu College of Science Jiujiang University Jiujiang 332000 People’s Republic of China Jiangxi Province Key Lab of Microstructure Function Materials Jiujiang 332000 People’s Republic of China Xinjiang Astronomical Observatory Chinese Academy of Sciences Urumqi 830011 People’s Republic of China Key Laboratory of Radio Astronomy Chinese Academy of Sciences Nanjing 210008 People’s Republic of China Institute of Physics Hunan University of Science and Technology Xiangtan Hunan 411201 People’s Republic of China

We obtain a sample of 1192 type-I quasars with the UV-optical, radio, and x-ray waveband coverage, which combined with the data from Huang and Chang [Mon. Not. R. Astron. Soc. 515, 1358 (2022)] and other matching objects of SDSS-DR16 with FIRST, XMM-Newton, and Chandra Source Catalog, and a sample of 407 flat-spectrum radio-loud quasars of blazars from the Roma-BZCAT, which can be used to investigate their multiband luminosity correlations and measure the luminosity distances of these type-I radio-loud quasar (RLQ) samples. We check the correlation between x-ray, UV-optical, and radio luminosity for various groupings of radio-quiet quasars (RQQs) and RLQs by parametrizing x-ray luminosity as a sole function of UV-optical or radio luminosity and as a joint function of UV/optical radio luminosity, which also can be employed to determine these cosmological distances. By Bayesian information criterion, the data suggest that the x-ray luminosity of RQQs is indirectly correlative with radio luminosity because of the connection between UV-optical and radio luminosity. However for RLQs, the x-ray luminosity is directly related to radio luminosity, and the correlations between x-ray, optical/UV, and radio luminosity get stronger with the increase in the ratio of monochromatic luminosities. Furthermore, we compare the results from RLQs with different UV-optical power-law index ΓUV, and find that the goodness of fit for RLQs with ΓUV≤1.6 is tentatively better. Finally, we apply a combination of type-I RLQs and Type Ia supernova (SN Ia) Pantheon to verify the nature of dark energy concerning whether or not its density deviates from the constant, and the statistical results indicate that the Lambda cold dark matter model may be in tension with type-I RLQs at ∼1.5σ.

关键词： Cosmological parameters Cosmology Dark energy Formation & evolution of stars & galaxies Optical, UV, & IR astronomy Active & peculiar galaxies Astrophysical jets Galactic nuclei & quasars

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