通讯机构：
[Gu, WJ ] Y;[Li, GX ] H;Yangtze Univ, Sch Phys & Optoelect Engn, Jingzhou 434023, Peoples R China.;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We investigate the scattering processes of two photons in a one-dimensional waveguide coupled to two giant atoms. By adjusting the accumulated phase shifts between the coupling points, we are able to effectively manipulate the characteristics of these scattering photons. Utilizing the Lippmann-Schwinger formalism, we derive analytical expressions for the wave functions describing two-photon interaction in separate, braided, and nested configurations. Based on these wave functions, we also obtain analytical expressions for the incoherent power spectra and second-order correlation functions. In contrast to small atoms, the incoherent spectrum, which is defined by the correlation of the bound state, can exhibit more tunability due to the phase shifts. Additionally, the second-order correlation functions in the transmission and reflection fields could be tuned to exhibit either bunching or antibunching upon resonant driving. These unique features offered by the giant atoms in waveguide QED could benefit the generation of nonclassical itinerant photons in quantum networks.
摘要：
Subnatural-linewidth single photons are of vital importance in quantum optics and quantum information science. According to previous research, it appears difficult to utilize resonance fluorescence to generate single photons with subnatural linewidth. Here we propose a universally applicable approach to generate fluorescent single photons with subnatural linewidth, which can be implemented based on Lambda-shape and similar energy structures. Further, the general condition to obtain fluorescent single photons with subnatural linewidth is revealed. The single -photon linewidth can be easily manipulated over a broad range by external fields, which can be several orders of magnitude smaller than the natural linewidth. Our study can be easily implemented in various physical platforms with current experimental techniques and will significantly facilitate the research on the quantum nature of resonance fluorescence and the technologies in quantum information science. (c) 2024 Chinese Laser Press
通讯机构：
[Huang, GM ] C;Cent China Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
scalar magnetometer;subsea power cables;attitude-independent detection;route tracking;high sea condition
摘要：
<jats:p>To overcome the shortcoming wherein the accuracy of subsea cable detection can be affected by the determination of the bias vector, scale factors, and non-orthogonality corrections of the vector magnetometer, a real-time attitude-independent route tracking method for subsea power cables is investigated theoretically and experimentally by means of scalar magnetic field checking. The measurement of the magnetic field Bc produced by the current in a cable is made immune to the influence of the platform attitude by extracting the component of Bc along the geomagnetic field using a high-bandwidth self-oscillating optically pumped magnetometer. The self-oscillating frequency is proved to be independent of the attitude of the magnetometer with the theoretical model. Experiments are carried out to test the attitude-independent performance, and the effectiveness of route tracking is verified by the results of the sea experiment. The proposed method will effectively improve the ability to locate subsea cables under high sea conditions.</jats:p>
通讯机构：
[Li, GX ; Huang, GM] C;Cent China Normal Univ, Sch Phys Sci & Technol, Wuhan 430079, Peoples R China.
关键词：
Absorption spectrum;magnetic resonance signal;multipole moment master equations;optically pumped magnetometer
摘要：
Self-oscillating magnetometers with high sensitivity are widely used in fields such as biomedicine and remote sensing. However, few studies comprehensively consider the effect of different parameters on their performance. We examined the effects of laser intensity, resonance detuning, radio frequency (RF) magnetic field, and atomic cell on the performance of portable self-oscillating magnetometers. To obtain the atomic absorption spectrum, we solved the system's master equation in the multipole moment form. In theory, we analyse the influencing factors on the atomic magnetic resonance (AMR) signal. In the experiment, we artificially varied the relevant parameters to control the trends of changes in the atomic absorption spectra and evaluated their performance. The results are beneficial for optimizing the parameters of portable self-oscillating magnetometers with a laser pump-probe structure.
作者机构：
[Huang, Guangming; Li, Gaoxiang; Tang, Wangwang] Cent China Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;[Yang, Guoqing] Hangzhou Dianzi Univ, Coll Elect & Informat, Hangzhou 310018, Peoples R China.
通讯机构：
[Huang, GM ] C;Cent China Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
magnetic target localization;magnetic gradient tensor;localization dead zone;eigenvector constraints
摘要：
<jats:p>Magnetic target localization using the magnetic gradient tensor (MGT) plays a significant role in underwater localization. However, this method inherently has a localization dead zone, which presents challenges for real-world applications. This paper delves into the root cause of this dead zone, identifying the non-invertibility of the MGT when the magnetic moment vector is orthogonal to the position vector from the target to the observation point. To tackle this issue, a method based on the eigenvector constraints is proposed. By constructing an objective function with eigenvector constraints and leveraging the property that its gradient at the observation point is zero, we derive an equivalent expression for the inverse of MGT that always holds and further develop a dead-zone-free localization method. To validate the robustness and efficacy of the proposed localization method, a comparative analysis with other methods is conducted. Simulation results in a 10 m × 10 m area under Gaussian noise demonstrate the proposed method’s capability to eliminate the dead zone and achieve an average localization error of 0.032 m. Experimental results further demonstrate that the proposed method eliminates the localization dead zone and exhibits greater robustness than the dominant method in the normal region. In summation, this paper provides an effective method for eliminating localization dead zone, offering a more stable and reliable method for magnetic target localization in practice.</jats:p>
摘要：
Atom-based mixers have been shown to be very useful in performing the absolute measurement of the magnitude of a radio-frequency (rf) field by using Autler-Townes (AT) splitting. However, there has been less success in measuring the phase of a rf field with the AT splitting in a magnetic-resonance system. The phase of the rf magnetic field plays a very important role in imaging applications. Here, we design an atomic mixer for measuring the phase of the rf field by detecting the transmission spectra of a laser-detected magnetic-resonance system based on the interference between Raman and cascade two-photon processes for Fg = 4 of the D1 line of cesium atoms. A scheme of measuring the rf phase can be realized with the elimination of the ac Zeeman shift of the system by adjusting the amplitude ratio of a transverse fundamental-wave field and its third-harmonic field. Theoretical and experimental results show that the scheme with cancellation of the ac Zeeman shift is superior in linear measurement of the longitudinal rf component. Our results provide schemes for a magnetic sensor based on quantum interference of nonlinear processes for the absolute measurement of the relative phase of rf fields.
通讯机构：
[Li, GX ] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We focus on the influence of multiphoton effect on the fluorescence spectrum and photon statistics of the bichromatically driven two-level atomic system. The influence of the multiphoton effect of the weaker driving field on the system and spontaneous emission are revealed by Schrieffer-Wolff perturbation theory, respectively. The physical origin of the multiphoton process affecting the fluorescence spectral asymmetry characteristics is fully investigated by studying the population distribution and the dressed atomic transition weight. Further, the suppression condition of the central peak of the central band is investigated. The photon statistical properties of the system are revealed by studying the frequency-resolved correlations between different sidepeaks and the central peak and sidepeak, respectively. In particular, the physical picture of the asymmetry of the two-photon correlation signal that is affected by the multiphoton process of the weaker driving field affecting the timing detection is fully revealed by the two methods of correlation moment and conditional quantum state, respectively. These results of ours provide a theoretical approach for studying multiphoton processes in multichromatically driven quantum systems, as well as for developing quantum simulation techniques such as spin locking.
摘要：
The resonance fluorescence properties in the steady-state regime are investigated for a driven cascaded exciton-biexciton quantum dot coupled to the two-dimensional black phosphorus metasurfaces. It is shown that for the material parameters under consideration, both the elliptic and hyperbolic dispersion patterns of the surface plasmon modes are achievable according to the variation of the carrier concentration. Further study on the Purcell factor indicates unequal enhancements in the spontaneous decay of the orthogonal in-plane dipoles. Motivated by this intriguing phenomenon, we then investigate the steady-state properties of the driven quantum dot, where the populations of the dressed levels are highly tunable by engineering the anisotropy of the surfaces. As a result, the manipulation of the carrier concentration will lead to strong modifications in the resonance fluorescence. Under certain conditions, one can observe the squeezing of two-mode noise spectra with different resonances and polarizations. Although at the expense of declines in the photon-sideband detunings, it is feasible to enhance the two-mode squeezing by gate doping. Our proposal can be easily extended to other hybrid systems containing anisotropic metasurfaces, which are important for the development of quantum information science. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
通讯机构：
[Guangming Huang] D;Department of Physics, Central China Normal University, Wuhan 430079, China<&wdkj&>Author to whom correspondence should be addressed.
摘要：
With the demand for fast response of magnetic field measurement and the development of laser diode technology, self-oscillating laser-pumped atomic magnetometers have become a new development trend. In this work, we designed a portable self-oscillating VCSEL-pumped Cs atom magnetometer, including the probe (optical path) and circuits. The signal amplification and feedback loop of the magnetometer, VCSEL laser control unit, and atomic cell temperature control unit were realized. We tested the performance of the magnetometer in the metering station. Finally, The performance of the VCSEL-pumped magnetometer designed in this work was compared with that of a CS-3 lamp-pumped self-oscillating atomic magnetometer; their performance was found to be mostly in the same order of magnitude, while the power consumption of our magnetometer was 3 W less than that of the CS-3. This work represents an exploratory attempt to integrate and miniaturize a portable self-oscillating VCSEL-pumped Cs atomic magnetometer.
摘要：
We study the excitation conditions of the supported field modes, as well as the spontaneous decay property of a two-level quantum emitter coupled to photonic structures containing topological insulators (TIs) and left-handed materials. Within the proper field quantization scheme, the spontaneous decay rates of dipoles with different polarizations are expressed in forms of the Green's functions. We find that in the proposed structure, the variation in the topological magnetoelectric polarizability (TMP) has a deterministic effect on the excitation of different field modes. As the result, the spontaneous decay property of the quantum emitter can be engineered. For a dipole placed in different spatial regions, the spontaneous decay feature indicates a dominant contribution from the waveguide modes, the surface plasmon modes or the free vacuum modes. Moreover, a special kind of the surface plasmon modes displaying asymmetric density of states at the interfaces, becomes legal in the presence of nontrivial TIs. These phenomena manifest the feasibility in controlling dipole emissions via manipulations of the topological magnetoelectric (TME) effect. Our results have potential applications in quantum technologies relied on the accurate control over light-matter interactions. (C) 2022 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement
作者机构：
[Chen, Ai-xi; Peng, Ze-an] Zhejiang Sci Tech Univ, Dept Phys, Hangzhou 310018, Peoples R China.;[Li, Gao-xiang] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
The space-time connection between the Mollow cascaded transitions with time orderings and the spatially directional correlated emissions of Mollow photons is analyzed theoretically in a strong laser-dressed subwave-length two-atom antenna, which supports only two-level electric dipole transitions. It can be regarded as the most prototypical collective quantum radiator to exploit the space-time quantum characteristics of the Mollow physics of resonance fluorescence. By constructing the photon filtering dynamics from the dressed two-atom antenna to a pair of quantum sensors, the frequency-resolved spatial two-point two-time correlations of different Mollow spectral lines are examined analytically in terms of the quantum sensor modes. It is shown that a rich significance of spatial directionality lies in the time orderings of cascaded emissions between different Mollow spectral lines. This feature enables the time orderings of different Mollow spectral lines to be tailored geometrically and thus prepared deterministically to produce highly directional temporal bunching effects of the Mollow photons with giant nonclassicality only for a specific two-photon detection order. The dressed two-atom system is therefore able to operate as a highly directional atomic antenna that may provide versatile applications in the fields of atom-photon-based quantum precise measurement physics and Mollow spectroscopy.
通讯机构：
[Li, GX ; Huang, GM] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
摘要：
We theoretically investigate the magneto-optical rotation (MOR) effect in cesium atoms in the Voigt geometry, in which an off-resonance linearly polarized laser beam serves as both pump and probe. By calculating the detailed evolution of atomic multipole moments truncated to second-rank, alignment-to-orientation conversion (AOC) effects are observed in two hyperfine ground states. The mechanisms responsible for this effect are demonstrated. The tensor AC-Stark shift produced by the optical pumping generates a nonlinear effect, resulting in atomic alignment directly coupled to orientation, which enables spin orientation to be obtained. Simultaneously, spin-exchange collisions lead to atomic alignment and orientation transfer between two ground-state manifolds. Additionally, we present the analytical expression of atomic spin polarization described by atomic multipole moments, and the contributions of the AOC effect to the optical-rotation signals are discussed in different light power regimes. Our results can be helpful for guiding MOR experiments by refining and optimizing the parameters.
摘要：
<jats:title>Abstract</jats:title>
<jats:p>Frequency-resolved photon statistics of resonance fluorescence generated from a two-level system driven by a strong laser field and a weak laser field with equal frequencies are studied. The frequency resolution of fluorescent radiation is described by quantum filtering dynamics, which is simulated theoretically by two single-mode quantum optical cavities with tunable frequencies to scan the incident fluorescent radiation. By calculating the two-photon intensity–intensity correlation functions in terms of the cavity modes, we demonstrate that two-color strong correlations of resonance fluorescence can be generated not only between the opposite sidebands, but also between the central band and one of the sidebands: although both sidebands are broadened due to the perturbation of the weak laser field on the strong-field dressed atom. We emphasize that these properties are in contrast to the conventional case of the standard single-atom Mollow triplet. Moreover, if the resonance frequencies of the two filtering cavities are tuned appropriately, broadband two-color strong correlations are predicted, and the physical origin is revealed from the perspective of quantum interference of photon emission dynamics. This can be considered as a feasible scheme for the design of broadband non-classical light sources, and may be beneficial to the quantum precise detection of atomic and molecular dynamics via quantum optical spectroscopy.</jats:p>
通讯机构：
[Wei Fang] I;[Yaping Yang] M;MOE Key Laboratory of Advanced Micro-Structure Materials, School of Physics Science and Engineering, Tongji University, Shanghai, People's Republic of China<&wdkj&>Institute of Systems Science and Department of Physics, College of Information Science and Engineering, Huaqiao University, Xiamen, People's Republic of China<&wdkj&>MOE Key Laboratory of Advanced Micro-Structure Materials, School of Physics Science and Engineering, Tongji University, Shanghai, People's Republic of China
摘要：
This study proposes a nanophotonic structure that supports quantum interference (QI) between orthogonal decay channels in multilevel quantum emitters within the framework of the quantum master equation. The Green functions of the electric field are obtained by applying boundary conditions in the presence of two-dimensional metasurfaces. We demonstrate distinct in-plane excitation features of the surface plasmon modes (SPMs) with the anisotropic metasurfaces tailored to conductivity components. In particular, we observed that the Purcell factor of transitions with orthogonal polarizations experiences unequal enhancements, owing to the anisotropic propagation of the SPMs. This property depends only on the anisotropy of the metasurfaces; thus, it is easily manipulated. Using this platform and considering experimentally achievable material parameters, we predict a strong interference effect in three-level quantum emitters. In principle, this enables the generation of maximum QI. Our study provides a method for realizing QI systems and has potential applications in highly integrated, tuneable quantum devices.
通讯机构：
[Guang-ming Huang; Gao-xiang Li] D;Department of Physics, Huazhong Normal University, Wuhan, 430079 China
关键词：
alignment spectra;atomic magnetic resonance;generalized parity;periodically modulated systems
摘要：
Periodically modulated systems with parity symmetry have been extensively investigated in recent years and exhibited various novel phenomena and potential applications in quantum technologies. In this study, a pump-probe structure is used to observe the influence of generalized parity on the alignment spectra of magnetic resonance in a periodically biharmonic modulated warm atomic cesium ensemble. The alignment spectra are symmetric when the generalized parity of modulated Floquet atomic ensemble is present. The breaking of spectral symmetry is accompanied by the absence of generalized parity. The influence of generalized parity on atomic alignment polarization distribution is analyzed based on the perspective of the angular-momentum probability surface. A necessary and sufficient condition for generalized parity to maintain spectral symmetry is verified experimentally and theoretically, providing a new perspective to investigative complex periodic modulation system. The results are universally applicable to atomic and solid-state systems.
摘要：
Quantum systems with multiharmonic dressing have been extensively investigated and exhibited various novel phenomena and technologies by virtue of their robust electromagnetic response. Here we mainly investigate the self-generated longitudinal Floquet modulation phenomenon of an alignment-based magnetic-resonance system with pump-probe structure dressed by two different transverse radio-frequency (rf) fields in a warm atomic cesium ensemble, both theoretically and experimentally. The self-generated Floquet modulation includes first and second harmonics, which are contributed to by linear and nonlinear processes from the weak-dressed field, respectively. The self-generated Floquet modulation dresses the alignment absorption spectra into two continua. The asymmetry of each dressed continuum is due to the generalized parity symmetry of the system being broken by the second harmonic modulation. Moreover, the nonlinear modification effect of the weak rf field on the probe verifies the existence of the four-wave mixing process in the rf band. The analytical expression, establishment process, and asymmetry analysis of the continua are given concisely. Our results can be applied to the fields of precision magnetic-field measurement, quantum control, quantum simulation, and so on. In addition, because the physical mechanism is universal, it can be applied not only to an atomic ensemble, but also to solid-state devices.
摘要：
<jats:p>We theoretically and experimentally investigate the laser-detected magnetic resonance spectra dressed by a radio-frequency magnetic field in <jats:italic>F</jats:italic><jats:sub>
<jats:italic>g</jats:italic>
</jats:sub> = 4 of <jats:italic>D</jats:italic><jats:sub>1</jats:sub> line of cesium atoms. The analytical expression of the transmission spectrum for magnetic resonance dressed by a radio-frequency magnetic field is derived and has substantial agreement with the transmission spectra observed in the experiment. The theoretical prediction of the ratio of the amplitudes of the two sidebands with the detuning is basically consistent with the experimental data, which confirms the validity of the analytical expression. The separation between the two sidebands under resonance shows a highly linear proportion to the amplitude of the dressing field, which may provide a useful scheme for the measurement of radio-frequency magnetic field and magnetic imaging.</jats:p>
