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arXiv 2024年

作者： Zhu, Hai Yin, Xian-Li 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 Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

The giant-atom topological-waveguide-QED systems have recently emerged as a promising platform for manipulating light-matter interactions. The combination of the multiple-point couplings and topological phase effect could lead to rich physical phenomena and effects. Here, we study single-photon scattering in a Su-Schrieffer-Heeger (SSH) waveguide coupled to either one or two two-level giant atoms. We assume that each giant atom is coupled to the waveguide via two coupling points and hence there exist four and sixteen coupling configurations for the single-giant-atom case and two-giant-atom separate coupling case, respectively. By solving the single-photon scattering problem in the real space, we obtain the exact expressions of the single-photon scattering amplitudes. It is found that a single photon in the SSH waveguide can be completely reflected or transmitted by choosing proper coupling configurations, coupling-point distances, atomic resonance frequency, and dimerization parameter. In addition, under proper parameter conditions, the scattering spectra are periodically modulated by the coupling-point distances. We also find that the collective behavior of the two giant atoms can be adjusted by quantum interference effect and topological effect and that the single-photon scattering spectra can exhibit the Lorentzian, super-Gaussian, electromagnetically induced transparencylike, and asymmetric Fano line shapes for some coupling configurations. This work will inspire the development of controllable single-photon devices based on the giant-atom topological-waveguide-QED systems. Copyright © 2024, The Authors. All rights reserved.

关键词： Quantum interference phenomena

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Entangling two giant atoms via a topological waveguide

arXiv

引用

arXiv 2023年

作者： Luo, Wen-Bin Yin, Xian-Li Liao, Jie-Qiao Liao, Jie-Qiao 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 Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

The entanglement generation of two two-level giant atoms coupled to a photonic waveguide, which is formed by a Su–Schrieffer–Heeger (SSH) type coupled-cavity array is studied. Here, each atom is coupled to the waveguide through two coupling points. The two-atom separate-coupling case is studied, and 16 coupling configurations are considered for the coupling-point distributions between the two atoms and the waveguide. Quantum master equations are derived to govern the evolution of the two atoms and characterize atomic entanglement by calculating the concurrence of the two-atom states. It is found that the two giant-atom entanglement depends on the coupling configurations and the coupling-point distance of the giant atoms. In particular, the entanglement dynamics of the two giant atoms in 14 coupling configurations depend on the dimerization parameter of the SSH waveguide. According to the self-energies of the two giant atoms, it is found that ten of these 16 coupling configurations can be divided into five pairs. It is also showed that the delayed sudden birth of entanglement between the two giant atoms is largely enhanced in these five pairs of coupling configurations. This work will promote the study of quantum effects and coherent manipulation in giant-atom topological-waveguide-QED systems. Copyright © 2023, The Authors. All rights reserved.

关键词： Atoms

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Entanglement of two distinguishable atoms in a rectangular waveguide: Linear approximation with single excitation

arXiv

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arXiv 2020年

作者： Li, Jing Hu, Lijuan Lu, Jing Zhou, Lan Synergetic Innovation Center for Quantum Effects and Applications 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 College of Science Hunan University of Science and Engineering Yongzhou425199 China

We consider two two-level systems (TLSs) coupled to the vacuum of guided modes confined in a rectangular waveguide. Two TLSs are fixed at different points in the waveguide and initially share an excitation. For the energy separation of the TLSs far away from the cutoff frequencies of transverse modes, two coupled delay-differential equations are obtained for the probability amplitudes of the TLSs. The effects of the difference of TLSs' energy separations and the inter-TLS distance on the time evolution of the concurrence of the TLSs are examined. Copyright © 2020, The Authors. All rights reserved.

关键词： Cutoff frequency

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Controlling the superradiant phase transition in the quantum Rabi model

arXiv

引用

arXiv 2024年

作者： Xie, Xuan Liu, Cheng Jiang, Lin-Lin Huang, Jin-Feng 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

In the ultrastrong-coupling regime, the quantum Rabi model can exhibit quantum phase transition (QPT) when the ratio of the qubit transition frequency to the frequency of the cavity field approaches infinity. However, it is challenging to control the QPT in few-body systems because of the limited coupling strength and the A2 term. Here, we propose a practical scheme to manipulate the QPT of quantum Rabi model in the strong-coupling regime. By applying a periodic frequency modulation to the two-level system in a quantum Rabi model in the strong-coupling regime, an anisotropic quantum Rabi model with ultrastrong and tunable coupling strengths for rotating and counter-rotating terms is obtained. The ground state and excitation energy of this model, in terms of the modulation parameters, are studied. We find that the QPT of the quantum Rabi model can be observed in the strong-coupling regime and externally controlled by the modulation. Copyright © 2024, The Authors. All rights reserved.

关键词： Excitation energy

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Purely Quantum Nonreciprocity by Spatially Separated Transmission Scheme

arXiv

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arXiv 2024年

作者： Liu, Zhi-Hao Zhang, Guang-Yu Xu, Xun-Wei 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 Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha410081 China Institute of Interdisciplinary Studies Hunan Normal University Changsha410081 China

Nonreciprocal photon blockade is of particular interest due to its potential applications in chiral quantum technologies and topological photonics. In the regular cases, nonreciprocal transmission (classical nonreciprocity) and nonreciprocal photon blockade (quantum nonreciprocity) often appear simultaneously. Nevertheless, how to achieve purely quantum nonreciprocity (no classical nonreciprocity) remains largely unexplored. Here, we propose a spatially separated transmission scheme, that the photons transport in different directions take different paths, in an optical system consisting of two spinning cavities coupled indirectly by two common drop-filter waveguides. Based on the spatially separated transmission scheme, we demonstrate a purely quantum nonreciprocity (nonreciprocal photon blockade) by considering the Kerr nonlinear interaction in one of the paths. Interestingly, we find that the nonreciprocal photon blockade is enhanced nonreciprocally, i.e., the nonreciprocal photon blockade is enhanced when the photons transport in one direction but suppressed in the reverse direction. We identify that the nonreciprocal enhancement of nonreciprocal photon blockade is induced by the destructive or constructive interference between two paths for two photons passing through the whole system. The spatially separated transmission scheme proposed in the work provides a novel approach to observe purely quantum nonreciprocal effects. Copyright © 2024, The Authors. All rights reserved.

关键词： Photons

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Optimized mechanical quadrature squeezing beyond the 3-dB limit via a gradient-descent algorithm

arXiv

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arXiv 2024年

作者： Liu, Yu-Hong 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

The preparation of mechanical quadrature-squeezed states holds significant importance in cavity optomechanics because the squeezed states have extensive applications in understanding fundamental quantum mechanics and exploiting modern quantum technology. Here, we propose a reliable scheme for generating mechanical quadrature squeezing in a typical cavity optomechanical system via seeking optimal cavity-field driving pulses using the gradient-descent algorithm. We realize strong quadrature squeezing in a mechanical resonator that exceeds the 3-dB steady-state limit, even with a thermal phonon occupancy of 100. Furthermore, the mechanical squeezing can be ultrarapidly created within one mechanical oscillation period. We also obtain the optimal pulsed drivings associated with the created mechanical squeezings and analyze the mechanism for mechanical squeezing generation. This paper will promote the application of optimal quantum control in quantum optics and quantum information science. Copyright © 2024, The Authors. All rights reserved.

关键词： Quantum optics

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Dynamical emission of phonon pairs in optomechanical systems

引用

Physical Review A 2022年第5期105卷 053507-053507页

作者： Fen Zou Jie-Qiao Liao Yong Li Beijing Computational Science Research Center Beijing 100193 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 Hunan Normal University Changsha 410081 China Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal University Changsha 410081 China Center for Theoretical Physics and School of Science Hainan University Haikou 570228 China

The 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 communication.

关键词： Optomechanics Photon statistics

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Sensing Based on Quantum Correlation of Photons in the Weak Nonlinear Regime

arXiv

引用

arXiv 2024年

作者： Yin, Zi-Qiang Liu, Zhi-Hao Tang, Jian Jing, Hui 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

Quantum correlation of photons based on quantum interference, such as unconventional photon blockade (UPB), has been extensively studied for realizing single-photon sources in weak nonlinear regime. However, how to use this effect for other practical applications is rarely studied. Here, we propose schemes to realize sensitive sensing by the quantum correlation of photons based on quantum interference. We demonstrate that UPB can be observed in the mixing field output from a Mach–Zehnder interferometer (MZI) with two cavities in the two arms based on quantum interference. We show that the second-order correlation function of the output field is sensitive to the parameters of system, and propose schemes to realize angular velocity and temperature sensing by measuring the second-order correlation of the photons output from the MZI. We find that the second-order correlation function of the output field is much more sensitive to the parameters of system than the mean photon number, which provides an application scenario for the quantum correlation of photons in sensitive sensing. Copyright © 2024, The Authors. All rights reserved.

关键词： Quantum interference devices

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Dark-Mode Theorems for Quantum Networks

arXiv

引用

arXiv 2023年

作者： Huang, Jian Liu, Cheng Xu, Xun-Wei 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

We propose and prove two theorems for determining the number of dark modes in linear two-component quantum networks composed of two types of bosonic modes. This is achieved by diagonalizing the two sub-networks of the same type of modes, mapping the networks to either a standard or a thick arrowhead matrix, and analyzing the linear dependence and independence between the column vectors associated with degenerate normal modes in the coupling matrix. We confirm the two theorems by checking the simultaneous ground-state cooling of the mechanical modes in linearized optomechanical networks. These results also work for linear fermionic networks and other networks described by quadratic coupled-mode Hamiltonian. The present method can be extended to study the dark-state effect in driven atom systems and to construct large decoherence-free subspaces for processing quantum information. This work will initiate the studies on dynamical, transport, and statistical properties of linear networks with decoupled subspaces. Copyright © 2023, The Authors. All rights reserved.

关键词： Linear networks

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Prediction of giant and ideal Rashba-type splitting in ordered alloy monolayers grown on a polar surface

arXiv

引用

arXiv 2020年

作者： Chen, Mingxing Liu, Feng 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 ChangshaHunan410081 China Department of Materials Science and Engineering University of Utah Salt Lake CityUT84112 United States

A large and ideal Rashba-type spin-orbit splitting is desired for the applications of materials in spintronic devices and the detection of Majorana Fermions in solids. Here, we propose an approach to achieve giant and ideal spin-orbit splittings through a combination of ordered surface alloying and interface engineering, that is, growing alloy monolayers on an insulating polar surface. We illustrate this unique strategy by means of first-principles calculations of buckled hexagonal monolayers of SbBi and PbBi supported on Al2O3(0001). Both systems display ideal Rashba-type states with giant SO splittings, characterized with energy offsets over 600 meV and momentum offsets over 0.3 Å−1, respectively. Our study thus points to an effective way of tuning spin-orbit splitting in low-dimensional materials to draw immediate experimental interest. Copyright © 2020, The Authors. All rights reserved.

关键词： Monolayers

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