Optical lattice atomic clocks play a crucial role in the field of quantum precision measurement due to their excellent characteristics, such as ultra-high frequency resolution for clock transition detection, extremely high frequency stability and accuracy, optical frequency domain clock transitions, pure atomic initial state preparation, and ultra-long quantum state coherence time. Taking advantage of the sensitivity of the clock transition frequency of optical lattice atomic clocks to physical quantities such as electric field, magnetic field, temperature, and gravitational acceleration, experiments can be designed to quantitatively determine the relationship between the quantities to be measured and the clock transition frequency and transition rate, and then combining with relevant theoretical frameworks to infer the value of the quantities being measured. This paper reviews the typical applications of optical lattice atomic clocks in quantum precision measurements, including time-frequency measurement, the test of general relativity, the measurement of the variation of fundamental physical constants with time, and atomic physics research.

Ellipsometers are essential tools used to measure the optical properties of samples, such as thin film thickness, optical constants of samples and structural profiles, by measuring the change in polarization state of polarized light before and after passing through the samples, which have wide applications in various fields, including physics, chemistry, materials science, and so on. Currently, the integration of new light sources with ellipsometry to enhance the performance of ellipsometers and expand their application scope is one of the hotspots in related research fields. Due to their unique non-classical properties and high signal-to-noise ratio, quantum entangled light sources have attracted extensive attention in the field of quantum precision measurement. In recent years, research on the principles and applications of quantum ellipsometer, which combines quantum light sources and ellipsometry, has been increasing. The fundamentals and types of classical ellipsometers are reviewed firstly in this paper. Then, based on this, the basic principles and research progress of quantum ellipsometers are mainly introduced, followed with the prospects of their future development direction.

The quantum precision measurement technology based on the theory of quantum parameter estimation has attracted extensive attention due to its detection advantages beyond the standard quantum limit. In many application scenarios, it often involves the simultaneous and precise detection of multiple parameters. However, since the generators of multiple parameters to be estimated are generally non-commutative, this leads to a trade-off in the estimation precision among different parameters, making it challenging to achieve simultaneous optimal estimation for all parameters. In recent years, instead of preparing large-scale entangled states, squeezed states or designing complex quantum measurement schemes, researchers have started from the perspective of optimizing the evolution of quantum dynamics by introducing quantum control to each component of quantum dynamics systems to adjust the evolution of quantum states. This kind of method can achieve simultaneous optimal estimation of multiple parameters, so the trade-off between multiple estimation precisions can be overcome, and a better quantum Cramér-Rao bound can be reached. In this paper, we summarize the quantum multiparameter estimation methods based on feedback control, expound on the improvement effect of feedback control on the simultaneous optimal estimation of multiple parameters from multiple perspectives, and demonstrate the potential of this technology in practical applications. Finally, the future research trends of quantum multiparameter estimation are summarized and prospected.

The electric field measurement technology based on Rydberg atoms has significant advantages in sensitivity, operating frequency band, traceability and anti-interference, and is expected to replace the traditional antenna in radio communication technology. In recent years, sensing and communication technologies using Rydberg atoms have developed rapidly. The basic principle of electric field measurement based on Rydberg atom is electromagnetically induced transparency (EIT). By measuring the real-time response of EIT spectrum to carrier signal, Rydberg atoms can recover baseband signal without demodulation. This paper reviews the experimental progress in communication technologies based on Rydberg atomic antennas, including their capabilities in reconstructing amplitude-modulated and frequency-modulated signals, as well as carrier phase measurement. It also discusses the key factors affecting the channel capacity, instantaneous bandwidth, and sensitivity of Rydberg atomic antennas. Finally, the development direction of this technology is prospected.

The electric field measurement based on Rydberg atoms, due to its high sensitivity, large dynamic range, and broad spectral coverage, has broad application prospects in fields such as information communication, spectrum detection, and meteorological warning, and is expected to become one of the key technologies for next-generation electromagnetic spectrum sensing. With ongoing advancements in both theory and experiment, the sensitivity of electric field measurement based on Rydberg atoms is gradually approaching the quantum projection noise limit. This article outlines the principles of electric field measurement based on Rydberg atoms, and reviews the recent progress in both single-body and many-body electric field measurement based on Rydberg atoms.So far, researchers have continually optimized electric field measurement techniques based on electromagnetically induced transparency and Autler-Townes (AT) splitting, employing methods such as the homodyne detection technique, superheterodyne technique, repumping, and six-wave mixing. These approaches have improved the electric field measurement sensitivity of single-body systems to 3.98 nV·cm-1·Hz-1/2, and the phase measurement sensitivity to 2 mrad. In addition to single-body systems, many-body systems based on Rydberg atoms have also been widely applied in electric field measurements by using their criticality at the phase trasition point, and the measurement sensitivity in many-body systems is expressed using Fisher information. Techniques such as cavity-enhanced optical bistability and stochastic resonance enhancement have been employed in many-body electric field measurement, and recent studies demonstrate that a 6.6 dB improvement in electric field measurement sensitivity, as well as robust resistance to external noise, has been achieved.

Atomic shear interferometry is an emerging matter wave interferometric technique developed in recent years, which has demonstrated growing applications in fundamental physics and practical metrology due to its exceptional precision and real-time measurement capabilities. However, the tilt of the detection system represents one of the critical sources of systematic errors in high-precision atomic shear interferometric measurements. To address this challenge, we first make a comprehensive theoretical analysis and quantitative evaluation of the impact of detection system tilt on interferometric measurements, and then experimentally implement a two-stage strategy for tilt measurement: using the plumb line method during system installation and using the atomic interferometric phase shift method during operational measurements. Regarding to the plumb line method, the tilt measurement resolution is 0.6 mrad, and the overall measurement accuracy is approximately 1–2 mrad considering the influence of various types of errors. Regarding to the atomic interferometric phase shift method, we develop specialized phase shift reference systems to measure system tilts for different interferometer configurations. Specifically, for single-species atom interferometers designed for gravity, gravity gradient, and rotation measurements, we propose and implement the atomic interferometric phase shift method with simultaneous dual-internal-state detection, achieving a tilt measurement resolution of 0.3 mrad and reducing tilt-induced errors in gravity measurements to the level of 10-10 g. For dual-species atom interferometers used in equivalence principle tests, we develop an alternative detection atomic interferometric phase shift method for real-time monitoring, achieving a tilt measurement resolution of 0.3 mrad, and satisfying the differential gravity measurement requirements at the 10-13 g level. The research methods used in this paper will provide references for solving the problems of systematic errors caused by the tilt of the detection system in atomic shear interferometers.

The second-order photon correlation is fundamental and crucial for characterizing quantum statistical properties of optical fields. In this paper, the photon correlation characteristics of fluorescence emitted by cold atoms coupled with nanofiber waveguide modes are investigated and analyzed, and the impact of the number of atoms on the second-order photon correlation of the radiated fluorescence coupled into the nanofiber is experimentally explored in a cold atomic system. The results of the second-order photon correlation for the fluorescence collected from single-ended and dual-ended nanofiber show that, with the adjustment of the number of atoms in the cold atomic system, the single-ended second-order photon correlation transits from bunching to anti-bunching, while the dual-ended second-order photon correlation consistently maintains anti-bunching features. This research reveals the high-order photon correlation properties of the radiated optical field resulting from the interaction between cold atoms and nanofiber, and provides an experimental basis for the development of a cold-atom all-fiber quantum information platform.

This study proposes a kind of polymer optical fiber doped with organic-inorganic hybrid perovskite quantum dots for rapid and sensitive temperature sensing in high-conformity interactive scenarios. In the polymer optical fiber, methylammonium lead bromide (MAPbBr3) is encapsulated as the core with high-refractive-index polydimethylsiloxane (PDMS), to enhance the stability of MAPbBr3 quantum dots, and at the same time, low-refractive-index PDMS is used as the cladding to improve the sensor's photoluminescence collection efficiency. The experimental results show that the polymer optical fiber has a diameter of up to 1120 µm, a fracture strain exceeding 150%, and a mechanical strength exceeding 2.84 MPa, exhibiting characteristics of miniaturization and stretchability. The sensor leverages the temperature dependence of the fluorescence quenching efficiency of MAPbBr3 quantum dots, demonstrating a temperature sensitivity of -1.314%℃-1 within the range of 25 ℃–85 ℃, with a response time of only 4.5 s. Finally, studies on body temperature detection at different parts of the human body successfully validate the sensor's capability for rapid and sensitive temperature change detection. The research results provide a foundation for the subsequent realization of a low-cost, easy-to-fabricate, wearable device for real-time monitoring human body temperature.

Due to the high single-photon detection sensitivity and the characteristics of multiple pixels, single-photon detector arrays (SPDA) have been widely applied in the areas of single-photon radar, bioluminescence imaging, and so on. However, limited by fabrication technology, the photon detection efficiency of each pixel of SPDA presents a certain difference, which often leads to imaging distortion. To solve this problem, the reverse bias voltage of each single photon detector for a 4 × 4 SPDA has been optimized individually in this work, which increases the averaged photon detector efficiency by 1.77 folds and reduces the difference to 1/7 of that before adjustment. Then on this basis, a Fourier-domain imaging (FDI) scheme has been developed by performing Fourier transform on the photon arriving time of each single-photon detector and using Fourier transform amplitude as the imaging parameter. The results show that with FDI scheme, a reasonably good imaging with a contrast-to-noise ratio up to 2.29 can still be determined even under the condition that the ratio of the noise intensity to the signal intensity reaches 104, manifesting the strong noise-resistant feature of FDI. This work offers a new route for achieving single photon detector under complex and noisy environments based on SPDA.

Quantum sensors represent an ideal medium for electromagnetic spectrum detection, offering the potential to overcome the limitations of traditional spectrum measurement principles in response bandwidth and measurement sensitivity, and have broad application prospects. This paper presents an ultra-wideband continuous spectrum measurement system based on Rydberg atoms mixer, and mainly analyzes the impact of local oscillator radio frequency (RF) field on the signal-to-noise ratio (SNR) of beat-note in the non-resonant region. Utilizing atomic non-resonant superheterodyne technology, we realize to measure the electromagnetic wave spectrum with a certain frequency bandwidth on each Rydberg state. By rapid tuning of the local RF field and the coupling laser wavelength, the continuous electromagnetic spectrum measurement across the microwave (1–40 GHz) and terahertz wave(110–170 GHz) bands is realized, achieving a minimum measurable field strength of 0.32 μV/cm in the resonant region and 2.34 μV/cm at 40 GHz in the non-resonant region, with a dynamic range exceeding 70 dB and a frequency resolution less than 10 Hz. This work have verified that quantum sensors based on Rydberg atoms possess the characteristics of full-band and high-sensitivity electromagnetic spectrum response, laying a research foundation for the development of high-sensitivity atomic spectrometers.

Partial discharge (PD) refers to a physical phenomenon that local discharge occurs between two electrodes without forming a full connection or a bridge. Continuous PD activity can significantly shorten the lifespan of electrical equipment. Therefore, it is crucial to monitor and identify PD signals. Traditional methods for measuring PD signals are limited by the metal materials and size of the antennas used, making it difficult to achieve near field detection inside a equipment like switchgear in substations, which limits the improvement of measurement sensitivity. This paper proposes a novel method for measuring PD signals based on Rydberg atoms, which allows for in situ near-field high-sensitive non-metallic detection. In our experiment, one of the most common types of PD phenomenon, corona discharge, is selected for model preparation and measurement. Firstly, cesium atoms are excited to the Rydberg state by two-photon excitation, and then the corona discharge signals are measured based on AC-Stark effect of Rydberg atoms. Finally, the measurement results are analyzed using the phase-resolved partial discharge spectroscopy method, and the phase distribution characteristics of the corona discharge and the distribution of discharge pulses are obtained.

Frequency calibration is a key step in analyzing the spectral frequency shift of electromagnetically induced transparency (EIT) in precision electric field measurements with Rydberg atoms. It is well known that minor frequency shift error (MHz magnitude) in the measurement can lead to significant changes of the field strength inversion results, and if the calibration accuracy is insufficient, the electric field inversion error will be nonlinearly amplified. In this paper, a frequency calibration method based on the saturated absorption spectrum of cesium atom D2 line is proposed, in which six characteristic absorption spectral peaks of cesium atom 6S1/2→6P3/2 transition are captured by designing a back propagation pump-probe optical path, and a time-frequency conversion model is constructed based on the inherent transition frequency of cesium atoms. The experimental results show that the frequency measurement error obtained by this method is kept within 1%, and the frequency calibration coefficient is obtained by multi-peak collaborative calibration. The method is further applied to the electric field measurement of EIT-Stark effect of Rydberg atoms, and it is shown that the fitting accuracy of the quadratic relationship between the frequency shift caused by the external electric field and the field strength is 0.997, with a measurement error less than 0.74%. Compared with the traditional single-peak calibration scheme, the method proposed in this work can greatly improve the anti-interference ability and calibration efficiency in complex noise environment by using the multi-peak collaborative calibration strategy.

In traditional binary frequency shift keying (2FSK) modulation, broad sidebands in the microwave signal indirectly impact alkali metal atom transitions at different optical frequencies, which will limit the accuracy of coherent population trapping (CPT) atomic clock. This paper proposes a microwave modulation method based on discrete sine wave frequency modulation (DSWFM), which uses direct digital modulation for dynamic carrier hopping, significantly narrowing the spectral sidebands. The measured results show that compared with the traditional 2FSK modulation, the frequency stabilities of CPT atomic clock at 1 s, 10 s, and 100 s intervals based on DSWFM modulation are improved by about 17%, 36% and 48%, respectively.