Abstract:This article provides a brief overview of the theoretical models of anomalous interactions and axionlike dark matter. It reviews the technical approaches of domestic and foreign researchers in recent years, including atomic magnetometers and comagnetometers, for exotic spin?dependent forces detection and dark matter searches. The article summarizes the experimental results regarding spin?velocity dependent interactions, spin?gravity interactions, and the coupling strength between the gradient of axionlike dark matter field and nucleons. On this basis, it provides an outlook for the future development direction in this field. By analyzing and suppressing systematic errors, and exploring new experimental schemes, it is expected to provide more stringent constraints for the coupling parameter space of spin?dependent forces, and to establish more rigorous limits of the coupling between axionlike dark matter and standard model fermions within a broader mass range.

Abstract:Magnetometry is an indispensable technology in human society. Magnetometers based on quantum sensing technologies have been developed in many quantum systems to realize high spatial resolution and sensitivity. Nitrogen?vacancy (NV) center in diamond is one of the quantum systems. This article provides an overview of the precision magnetic measurement technology based on the NV center system and its applications in various fields. Principles and advantages of using the NV center for magnetic field measurement are included in this paper. The research status of the magnetometry is also presented. Besides, practical applications of the magnetometry based on NV center in the field of materials imaging and life sciences are demonstrated. In the future, the magnetometry based on NV center will play an important role in the development of high sensirivity and spatial resolution vector magnetometer and facilitate more applications as geomagnetic mapping, nondestructive testing and others

Abstract:The applications of whispering?gallery?mode microcavities in sensing research, including displacement sensing, force sensing, acceleration sensing, mass sensing, nanoparticle sensing, temperature sensing, angular velocity sensing and exceptional points enhanced sensing, in recent years have been reviewed. The basic theory of different sensing schemes and some related important experimental work are introduced, and the important factors that may help improve sensing accuracy are illustrated, which will provide reference for the following theoretical and experimental research.

Abstract:Quantum metrology is a technology to enhance the accuracy and sensitivity of parameter estimation by using quantum superposition and entanglement, quantum interaction process and quantum measurement. It is one of the most promising quantum technologies in the short and medium term. Starting from the optimization research scheme of quantum metrology, we analyze three optimization schemes of quantum metrology by combing and summarizing related literatures, which are categorized into: quantum state preparation and measurement, the control of quantum evolution process and the classical post?processing optimization. The latest theoretical and experimental progresses of quantum metrology are introduced. Finally, the problems and challenges of quantum metrology are summarized, and the further work is prospected.

Abstract:Faraday laser is a novel external cavity diode laser (ECDL) that uses the Faraday anomalous dispersion optical filter as the frequency?selective element. In principle, the changes of Faraday laser output wavelength with the laser diodes' temperature and current always corresponds to the atomic transition lines. The laser frequency can be effectively locked to the atomic transition spectral line, achieving a narrow linewidth laser output signal. Both short?term and long?term frequency stability are good enough for some applications. The development process of Faraday anomalous dispersion optical filters, and the mechanism, development process and advantages of Faraday lasers are summarized in this paper since the Faraday effect was reported in 1845. Combined with the research results at home and abroad, the technical bottlenecks and corresponding solutions belonging to different stages of Faraday laser development are introduced. The important value of Faraday laser in the quantum field, especially in the field of quantum precision measurement, in the future is also anticipated.

Abstract:This article summarizes the basic principles of electric field sensing technology based on Rydberg atoms, and analyzes the advantages of Rydberg atomic electric field measurement, such as high sensitivity, broadband, traceability to the International System of Units (SI), and high spatial resolution. The effects of laser parameters, detector noise, environmental electromagnetic interference, and other factors on the sensitivity and frequency response bandwidth of Rydberg atomic field strength measurement were discussed. Methods to improve the sensitivity of field strength measurement, such as frequency modulation, re pumping, and parameter optimization, were introduced, and methods to enhance the frequency response bandwidth of measurement, such as single auxiliary field atomic heterodyne method and double auxiliary five level heterodyne method, were elaborated. Explored the application of Rydberg atomic electric field sensing technology in metrology, communication, radar, imaging, and other fields, and pointed out that the sensitivity of Rydberg atomic electric field measurement should be further improved by optimizing the atomic gas chamber structure, designing high?performance photodetectors, and improving the performance of optical cavities; We should conduct in?depth research on the sources of uncertainty in the measurement of the Rydberg atomic electric field, and conduct comprehensive testing and characterization of the Rydberg atomic sensor; The miniaturization and engineering design research of the Rydberg atomic electric field measurement related devices should be carried out to further improve the practical application performance of the Rydberg atomic electric field measurement technology.

Abstract:Atomic magnetometer is a precision measurement instrument based on quantum technology. Due to its extensive application potential, it is becoming the domestic and worldwide cutting?edge research. Atomic magnetometer concerns many quantum theories, and a grasp of the basics is helpful to carrying out the magnetometer related work and going in for a deeper research in the related areas. The author summaries some of the elementary quantum physics involved in the atomic magnetometer, including optical pumping, light shift, optical detection, evolution of atomic polarization in magnetic field, and magnetic resonance, etc.

Abstract:This paper outlines the basic principles of two?photon transition, and then introduces the experimental progress of two?photon optical frequency standards excited by continuous?wave and pulsed laser. Developing the lasers with higher power and lower frequency noise to suppress shot noise and intermodulation noise is the most effective way to improve the short?term stability of two?photon optical frequency standards which is limited by the performance of local oscillators. Finally, this paper summarizes the applications of two?photon optical frequency standards in science and engineering. The measurement of energy level spacing of hydrogen based on two?photon direct comb spectroscopy has become one of the most important techniques to measure Rydberg constant and proton charge radius, and plays an essential role in the test of quantum electrodynamics. The combination of two?photon optical frequency standard and microresonator?based optical frequency comb will pave the way for the miniaturization and integration of optical atomic clocks.

Abstract:The mercury ion trapped microwave frequency standard is pumped by the mercury lamp, and can achieve miniaturization. It has potential wide applications for the future satellite navigation, deep space explorations and time keeping for its advantages of small volume and high performance indicators. In order to improve pumping efficiency and reduce noise background, it is necessary to carry out optical design of mercury lamps, so that the pumping light can fully interact with trapped ions through the center of the quadrupole trap well while reducing reflection from the vacuum cavity and quadrupole rods. Firstly, two optical design methods, occlusion light source method and non proportional amplification method, are proposed. Then, the specific design process and results of the two design methods were introduced, and the energy utilization efficiency of the two optical design methods for mercury lamps was compared. Finally, the non proportional amplification method was used for optical path optimization design, and physical system signal detection experiments were completed. The experimental results show that using this optical design scheme, the amplitude of mercury ion light microwave dual resonance transition signal has been increased by more than 20%.

Abstract:The traditional atomic interference gravimeter, Mach?Zender type atomic gravimeter, has the problem of large volume, which affects the portability of the equipment. Peking University realizes the first compact atomic interference gravimeter based on the Bloch oscillation principle of moving optical lattice in China which is different from the conventional Mach?Zehnder atomic gravimeter. The sampling rate of the experimental system reaches 0.9 Hz, which can meet the needs of long?term real?time measurement，and the vertical displacement of atoms in the experimental system is about 3 cm. The sensitivity measured by the system reaches 4.6 × 10² μGal·Hz^-1/2. The resolution can reach 6.5(0.7) μGal in 2 800 s integration time. The experimental results point the future development direction for miniaturization and application of atomic interference gravimeter.

Abstract:Absolute gravity measurement plays an important role in the field of railway subgrade detection, but most mobile gravimeters have complex structures or mediocre accuracy, and their application range is limited. In this paper, we integrate a system of movable absolute gravity measurement on the rail, which realizes highly integrated system structure design and automatic test process, and undertake experiments of absolute gravity measurement in the laboratory and on the rail. Firstly, in the laboratory, the long?erm gravity measurement sensitivity is 440 μGal?Hz-1/2 and the measurement accuracy is 30 μGal in the integration time of 300 s. Secondly, on the outdoor rail, the uncertainty of movable gravity measurement is less than 15 μGal, and the measurement deviation with the relative gravimeter (LG-1) is less than 40 μGal. Lastly, the gravity measurement sensitivity on the rail is about 707.9 μGal?Hz-1/2. Therefore, our system can realize fast gravity measurement under outdoor conditions and provide new instrument and solution for detection of railway subgrade.

Abstract:In view of the confusion of using different Allan variance to analyze the sensitivity of atomic interferometer, this paper systematically gives the detailed derivation of Allan variance, overlapping Allen variance and modified Allan variance in time domain and frequency domain, analyzes their resolution to five kinds of typical noise, and points out that the modified Allan variance is more suitable for evaluating the long?term stability of atomic interferometer. Based on the expression of modified Allan variance in frequency domain, the transfer function between sensitivity and noise power spectrum of atomic interferometer with measurement dead zone is given for the first time. By analyzing its characteristics, two specific ways to improve the sensitivity of atomic interferometer are pointed out. These studies have laid a more solid theoretical foundation for the further development and evaluation of atomic interferometer technology.

Abstract:In order to solve the problems of difficult quantitative filling and poor stability of alkali atoms during the preparation of atom vapor cells, alkali atom vapor cells with different RbN₃ decomposition time were prepared by micro?electro?mechanical system (MEMS) technology combined with photodecomposition of alkali azide, specifically by deep silicon etching, quantitative filling of RbN₃ solution, double anode bonding and ultraviolet irradiation. The atom vapor cells with different RbN₃ decomposition time were tested with a self?built absorption spectrum testing device. The influences of different RbN₃ decomposition time on the Rb vapor absorption peak intensity, half?height width and frequency shift in the atom vapor cells were studied. Though experiments and theoretical analysis, it is found that when the RbN₃ decomposition time is 3.5 h, the Rb atom absorption peak intensity is the largest, which can meet the requirements of high quality atom vapor cell preparation. It provides important technical reference for the preparation of high quality atom vapor cells, and lays the foundation for promoting the development of chip based measurement and sensing technology based on MEMS atom vapor cell.

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