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Quantum phase transition of the Jaynes-Cummings model

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Science China(Physics,Mechanics & Astronomy) 2024年第1期67卷 1-9页

作者： Cheng Liu Jin-Feng Huang 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 ApplicationsInstitute of Interdisciplinary StudiesHunan Normal UniversityChangsha 410081China

Herein,we propose an experimentally feasible scheme to show the quantum phase transition of the Jaynes-Cummings(JC)model by modulating the transition frequency of a two-level system in a quantum Rabi model with strong coupling.By tuning the modulation frequency and amplitude,the ratio of the effective coupling strength of the rotating terms to the effective cavity(atomic transition)frequency can enter the deep-strong coupling regime,while the counter-rotating terms can be neglected.Thus,a deep-strong JC model is obtained.The ratio of the coupling strength to resonance frequencies in the deep-strong JC model is two orders of magnitude larger than the corresponding ratio in the original quantum Rabi model.Our scheme can be employed in atom-cavity resonance and off-resonance cases,and it is valid over a broad range.The nonzero average cavity photons of the ground state indicate the emergence of a quantum phase transition.Further,we demonstrate the dependence of the phase diagram on the atom-cavity detuning and modulation parameters.All the parameters used in our scheme are within the reach of current experimental technology.Our scheme provides a new mechanism for investigating the critical phenomena of finite-sized systems without requiring classical field limits,thereby opening a door for studying fundamental quantum phenomena occurring in the ultrastrong and even deep-strong coupling regimes.

关键词： Jaynes-Cummings model quantum phase transition frequency modulation

Vibration measurement with frequency modulation single-pixel imaging

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Chinese Optics Letters 2023年第1期21卷 54-58页

作者：章文欣陶钰秀吴杨康祝福蔡文超刘宁赵强薛平 College of Electronic and Optical Engineering&College of Flexible Electronics(Future Technology) Nanjing University of Posts and TelecommunicationsNanjing 210023China State Key Laboratory of Low-Dimensional Quantum Physics and Department of Physics Collaborative Innovation Center of Quantum MatterTsinghua UniversityBeijing 100084China

Single-pixel imaging can reconstruct the image of the object when the light traveling from the object to the detector is scattered or distorted.Most single-pixel imaging methods only obtain distribution of transmittance or reflectivity of the object.Some methods can obtain extra information,such as color and polarization information.However,there is no method that can get the vibration information when the object is vibrating during the measurement.Vibration information is very important,because unexpected vibration often means the occurrence of abnormal conditions.In this Letter,we introduce a method to obtain vibration information with the frequency modulation single-pixel imaging method.This method uses a light source with a special pattern to illuminate the object and analyzes the frequency of the total light intensity signal transmitted or reflected by the object.Compared to other single-pixel imaging methods,frequency modulation single-pixel imaging can obtain vibration information and maintain high signal-to-noise ratio and has potential on finding out hidden facilities under construction or instruments in work.

关键词： single-pixel imaging frequency modulation vibration measurement

Carrier suppression in quadruple frequency modulation by cascaded optical external modulators for millimeter-wave generation

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Chinese Optics Letters 2009年第3期7卷 188-190页

作者：张伟冯雪张巍刘小明 State Key Laboratory on Integrated Optoelectronics Tsinghua National Laboratory for Information Science and TechnologyTsinghua University

The optical carrier suppression in optical quadruple frequency modulation by cascaded external modulators is investigated theoretically and experimentally. Theoretical analysis demonstrates that the optical carrier suppression ratio is related with not only the initial phase difference of electrical signals applied on the two modulators, but also the optical phase shift between the two modulators. The maximum suppression ratio can be achieved when the total phase difference is equal to nπ＋π/2 （n = 1, 2,…）, which is verified by experiments. By properly controlling the total phase shift, 40-GHz millimeter-wave is generated by using a 10-GHz radio frequency （RF） source and the modulators.

关键词： frequency modulation Millimeter wave devices Millimeter waves Phase shift

Suppression of Stokes heating processes and improved optomechanical cooling with frequency modulation

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Communications in Theoretical Physics 2022年第4期74卷 42-51页

作者： Yang Bao Qinghong Liao Qingmin Zhao Jing Wu Department of Electronic Information Engineering Nanchang UniversityNanchang 330031China State Key Laboratory of Low-Dimensional Quantum Physics Department of PhysicsFrontier Science Center for Quantum InformationTsinghua UniversityBeijing 100084China

Ground-state cooling of mesoscopic mechanical objects is still a major challenge in the unresolved-sideband regime.We present a frequency modulation(FM)scheme to achieve cooling of the mechanical resonator to its ground-state in a double-cavity optomechanical system containing a mechanical resonator.The mean phonon number is determined by numerically solving a set of differential equations derived from the quantum master equations.Due to efficient suppression of Stokes heating processes in the presence of FM,the ground-state cooling,indicated by numerical calculations,is significantly achievable,regardless of whether in the resolved-sideband regime or the unresolved-sideband regime.Furthermore,by choosing parameters reasonably,the improvement of the quantum cooling limit is found to be capable of being positively correlated with the modulation frequency.This method provides new insight into quantum manipulation and creates more possibilities for applications of quantum devices.

关键词： ground-state cooling Stokes heating processes frequency modulation unresolved sideband

Recognition of frequency modulation Signal Using Parameter Invariant Filter

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Journal of Shanghai University(English Edition) 2005年第5期9卷 415-418页

作者：姚亚峰陈建文黄载禄 Department of Electronics and Information Huazhong University of Science and Technology Wuhan 430074 P. R. China

To classify the frequency modulation signal, this paper employs a parameter invariant filter, which can transfer the frequency modulated information to variety of its envelope, and then extracts the histogram feature to classify the modulation type. This method can efficiently classify the type of a signal such as frequency modulation （FM）, binary frequency shift keyiing （BFSK）, quadrature frequency shift keying （QFSK）, 8-ary frequency shift keying （8FSK）, etc. It can easily be realized and is especially suitable to applications in software radio.

关键词： modulation recognition frequency modulation parameter invariant filter histogram.

Effects of modulation amplitude and frequency of frequency-modulated fiber lasers on the threshold of the stimulated Brillouin scattering in optical fiber

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Chinese Optics Letters 2010年第12期8卷 1124-1126页

作者：陈伟孟洲 College of Optoelectronic Science and Engineering National University of Defense Technology

Stimulated Brillouin scattering （SBS） is a key problem with the increasing power of fiber transmission systems. In this letter, a frequency-modulated fiber laser with an ultra-narrow linewidth is chosen as a light source. The SBS threshold is increased from 4.1 to 6.2 mW at 13-MHz frequency modulation amplitude for a 50-km G652 fiber. We also show that the SBS threshold increases with not only the frequency modulation amplitude, but also the modulation frequency. The modulation frequency should be high enough for effective modulation.

关键词： Electric power transmission Fiber lasers Fibers frequency modulation Light polarization Light sources Optical fibers Ultrasonics

frequency modulation of High-Speed Mill Chatter

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厦门大学学报（自然科学版） 2002年第S1期41卷 5-页

作者： WU Yun-xin, DUAN Ji-an (College of Mechanical-Electrical Engineering, Central-South University, Changsha 410083, China)

Mill chatter is a common phenomenon in the metal strip rolling process. Product defects caused by mill vibration were reported worldwide during last two decades, which is usually classified as torque vibration of the driving system with low frequencies and vertical vibration of the mill stand with comparative higher frequencies. The frequency range of the vertical vibration is wide (in general from more than 100 Hz to more than 1 000 Hz), and the vibration phenomena are very complex, even it is very difficult to determine the vibration causes, which is followed the name "ghost vibration". During a fieldwork to measure the vibration in high-speed rolling mills, a frequency modulation phenomenon was identified, which had not been reported in strip rolling community. This article makes a theoretical investigation to the newly encountered phenomenon in strip rolling process. According to an analysis of the mill roller bearings, the periodic change of stiffness of roller bearings at the fixed load orientation, together with the periodic change of the effective errors of the bearings, may cause amplitude and frequency modulation,based on the theories of Fourier series and Bessel function. The comparison between test results and theoretical analysis implies that the frequency modulation is caused by the effective errors of the mill roller bearings that have 12 ripples on the internal ring of the bearings.

关键词： rolling mill chatter frequency modulation

A giant atom with modulated transition frequency

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Frontiers of physics 2023年第1期18卷 209-218页

作者： Lei Du Yan Zhang Yong Li Center for Theoretical Physics and School of Science Hainan UniversityHaikou 570228China Beijing Computational Science Research Center Beijing 100193China Center for Quantum Sciences and School of Physics Northeast Normal UniversityChangchun 130024China Synergetic Innovation Center for Quantum Effects and Applications Hunan Normal UniversityChangsha 410081China

Giant atoms are known for the frequency-dependent spontaneous emission and associated interference effects.In this paper,we study the spontaneous emission dynamics of a two-level giant atom with dynamically modulated transition frequency.It is shown that the retarded feedback effect of the giant-atom system is greatly modified by a dynamical phase arising from the frequency modulation and the retardation effect itself.Interestingly,such a modification can in turn suppress the retarded feedback such that the giant atom behaves like a small one.By introducing an additional phase difference between the two atom-waveguide coupling paths,we also demonstrate the possibility of realizing chiral and tunable temporal profiles of the output fields.The results in this paper have potential applications in quantum information processing and quantum network engineering.

关键词： giant atoms frequency modulation spontaneous emission dynamics non-Markovian retardation effect

The optimal design for weak optical feedback semiconductor laser with frequency modulation

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Chinese Journal of Lasers 1992年第2期 17-22页

作者： Linlin LI (Zhengzhou University Zhengzhou 450052, PRC)

In this paper the frequency modulation characteristics the semiconductor laserwith weak optical feedback are presented,considering both the frequency deviation and thespurious intensity modulation.The frequency modulation can be realized without spurious in-tensity modulation under proper feedback conditions.There is an optimal feedback intensity tomaximize the frequency deviation.

关键词： frequency modulation spurious intensity modulation weak optical feedback