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Study on the One-year Accuracy of Pulsar time-scale

Research in Astronomy and Astrophysics 2025年第1期25卷 282-296页

作者： Linlin Wang Zhehao Zhang Chengshi Zhao Zongke Li Minglei Tong National Time Service Center Chinese Academy of Sciences Key Laboratory of Time Reference and Applications Chinese Academy of Sciences University of Chinese Academy of Sciences

Determining accurate pulsar timing model parameters is essential for establishing TT(PT), a realization of Terrestrial time (TT) based on a pulsar timescale (PT). This study discusses the impact of different data spans on the accuracy of pulsar timing model parameters when determining pulsar timing model parameters. Using observations of PSR J0437-4715, J1909-3744, J1713+0747, and J1744-1134 from the second data release of the International Pulsar Timing Array (IPTA II, Version A), we compare the accuracy of the timing model parameters determined by these observations with different data spans. The results show for PSR J0437-4715, J1713+0747,and J1909-3744, the amplitude fluctuations of rotational frequency remain within 10-15, 10-14, and 10-14Hz,respectively, when the data spans for determining pulsar timing model parameters exceed 13, 14, and 6 ***, the one-year accuracy of TT(PT) is crucial for its application in timekeeping. By comparing the frequency deviations of TT(PT) relative to TT(BIPM) under both ideal (kr) and actual (kp) conditions across different data spans, we find that when the data span reaches the duration above, the accuracy of TT(PT) surpasses that of TT(TAI) under ideal conditions, slightly inferior under actual conditions. This suggests with improved observational technologies, the accuracy of TT(PT) can be further enhanced.

关键词： (stars:) pulsars:individual (PSRs J1909-3744,J1713+0747,J0437-4715,J1744-1134) time methods:data analysis

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Report on 3,143.6-km time and Frequency Transfer Fiber Link with Ps-level Stability

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Chinese Physics Letters 2025年第1期42卷 68-72页

作者： Bo Liu Xinxing Guo Jiang Chen Yanli Zhou Tao Liu Ruifang Dong Shougang Zhang National Time Service Center Chinese Academy of SciencesXi'an 710600China University of Chinese Academy of Sciences Beijing 100039China Key Laboratory of Time Reference and Applications Chinese Academy of SciencesXi'an 710600China China Mobile Communications Group Shaanxi Co. LtdXi'an 710600China

This letter describes the implementation of a high-precision time and frequency transmission system using a two-way and wavelength division multiplexing scheme over 3,143.6 km of field fiber links,connecting 21 sites between Xi’an and Beijing,*** scheme incorporates a link noise clean-up system(LNCUS),wherein a controlled very-low-phase noise BVA oscillator acts as an internal frequency source at the relay site to effectively suppress the interference caused by the fiber link ***,the high-stability pulse generation technology in the LNCPS provides sufficient short-term stability to significantly improve the stability of the fiber time *** results indicate a time transfer stability in terms of time deviation(TDEV)of less than2.07 ps@1s,5.9 ps@100,000s,and combined uncertainty of less than 49.29 ps for the 3,143.6 km field fiber *** results represent a significant breakthrough in achieving high-accuracy time transfer and continuous operation over ultralong-span field optical fibers exceeding 3,000 km for the first *** enabled time transfer and synchronization services over the longest international optical fiber distance,thereby establishing a fundamental basis for constructing a nationwide high-precision time service through optical fiber networks.

关键词： fiber breakthrough exceeding

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Modulation of Bessel-like vector vortex beam using the resonant magneto-optical effect in rubidium vapor

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Chinese Physics B 2025年第2期34卷 274-280页

作者： Yan Ma Xin Yang Hong Chang Ming-Tao Cao Xiao-Fei Zhang Rui-Fang Dong Shou-Gang Zhang Key Laboratory of Time Reference and Applications National Time Service CenterChinese Academy of Sciences(CAS)Xi’an 710600China School of Astronomy and Space Science University of Chinese Academy of SciencesBeijing 100049China Ministry of Education Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter Shaanxi Province Key Laboratory of Quantum Information and Quantum Optoelectronic DevicesSchool of PhysicsXi’an Jiaotong UniversityXi’an 710049China Department of Physics Shaanxi University of Science and TechnologyXi’an 710021China Hefei National Laboratory Hefei 230088China

The Bessel-like vector vortex beam(BlVVB)has gained increasing significance across numerous ***,its practical application is restricted by manufacturing difficulties and polarization ***,the ability to manipulate its degrees of freedom is highly *** this paper,the full-domain polarization modulation of BlVVB within a hot atomic ensemble has been *** begin with the theoretical analysis of the resonant magneto-optical effect of atoms with a horizontal linear-polarized beam and experimentally demonstrate precise manipulation of the polarization state across the entire domain of the BlVVB,achieving an error margin of less than 3°at various cross-sectional *** study provides a novel approach for the modulation of BlVVB based on atomic media,which holds potential applications in sensitive vector magnetometers,optical communications,and signal processing.

关键词： Bessel-like vector vortex beam resonant magneto-optical effect polarization modulation Rb atomic ensemble

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Accuracy degradation rate of LEO satellite-predicted orbits using different POD methods

Accuracy degradation rate of LEO satellite-predicted orbits ...

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2025 International Technical Meeting of The Institute of Navigation, ITM 2025

作者： Liu, Jiawei Wang, Kan Chen, Beixi El-Mowafy, Ahmed Allahvirdi-Zadeh, Amir Yang, Xuhai National Time Service Center Chinese Academy of Sciences Xi'an China University of Chinese Academy of Sciences Beijing China Key Laboratory of Time Reference and Applications Chinese Academy of Sciences Xi'an China School of Earth and Planetary Sciences Curtin University Perth Australia

ISBN: (纸本)9780936406404

To achieve high-accuracy positioning and timing in real time using Low Earth Orbit (LEO) navigation signals, the precision of the orbital products is of high necessity. Reduced-dynamic LEO satellite Precise Orbit determination (POD) can nowadays provide near-real-time orbits with an accuracy of centimeters, and real-time users can rely on broadcast LEO satellite ephemeris based on short-term prediction. However, in the case of experiencing observation data problems or satellite manoeuvers that are not performed as planned, large orbital errors or residuals could hamper the orbits from passing the self-check, and accordingly reduce their availability to users. In such a case, the kinematic POD delivers a redundant option. This study assesses the degradation rate of accuracy and integrity of the predicted orbits by applying different POD methods. It supports the selection of the best orbital type for real-time ephemeris fitting based on their near-real-time POD accuracy and the degradation rate of the prediction accuracy with the prediction time, assuming that different types of orbits might be generated at various times and thus require different prediction times for real-time applications. In this contribution, using 6 days of GPS and GPS/Galileo-combined dual-frequency phase and code observations tracked onboard Sentinel-3B (orbital altitude of about 810 km) and Satellite-6A satellites (about 1340 km), three types of predicted orbits are assessed. The degradation rates of the Orbital User Range Errors (OUREs) are calculated for predicted reduced-dynamic (RP), batch least-squares kinematic (KP), and filter-based kinematic (TP) orbits under different scenarios. The prediction rates for the three approaches amount to 4.2, 8.2, and 3.1 cm/h, respectively, for Sentinel-3B, and 2.6, 5.0, and 4.0 cm/h, for Sentinel-6A under the best-case scenario. Moreover, the integrity is analyzed using the 68.3%, 95.5%, and 99.9% Confidence Levels (CLs). Within the 1 h of prediction ti

关键词： Orbits

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Nonlinear dynamics in an artificial feedback spin maser

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Physical Review A 2025年第2期111卷 023118-023118页

作者： Mingjun Feng Lan Wu Guobin Liu National Time Service Center Chinese Academy of Sciences Xi'an 710600 China School of Astronomy and Space Science University of Chinese Academy of Sciences Beijing 100049 China Key Laboratory of Time Reference and Applications Chinese Academy of Sciences Xi'an 710600 China

Spin masers with optical detection and artificial feedback are widely used in fundamental and practical applications. However, a full picture of the maser dynamics is still absent. By solving the feedback-driven Bloch equations, we simulated the dynamics of an ideal spin maser in a broad parameter space. Rich nonlinear dynamics including high-order-harmonic generation, nonperiodic spin oscillations, and frequency comb were revealed when the artificial feedback interaction exceeds the normal spin-field interaction. We also propose a pulse feedback spin maser protocol, which constructs an ultralow field magnetic frequency comb and could be useful in precision atomic magnetometers in searching for spin-dependent exotic interactions.

关键词： Spin dynamics

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Novel compensation technique for mitigating dispersion in fiber-optic microwave frequency transfer systems

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Chinese Optics Letters 2025年第2期 13-18页

作者：鱼少少赵文宇王鑫李杏花张首刚 Key Laboratory of Time Reference and Applications National Time Service Center Chinese Academy of Sciences University of Chinese Academy of Sciences

In this paper, a novel compensation technique is presented for mitigating dispersion in fiber optic microwave frequency transfer systems. By introducing an additional carrier light into the transmission link, the system effectively eliminates the effect of dispersion on temperature in the fiber link. The experimental results show that the long-term stability of microwave frequency transfer over a 100 km optical fiber link is better than 10-18/d. This remarkable result strongly demonstrates the feasibility of our proposed scheme, while also highlighting its significant practical significance in ensuring the long-term stability of microwave frequency transfer across hundreds of kilometers of optical fibers.

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Doppler Positioning Using Multi-Constellation LEO Satellite Broadband Signals as Signals of Opportunity

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Navigation, Journal of the Institute of Navigation 2025年第2期72卷

作者： Allahvirdi-Zadeh, Amir El-Mowafy, Ahmed Wang, Kan School of Earth and Planetary Sciences Curtin University GPO Box U1987 PerthWA6845 Australia National Time Service Center Chinese Academy of Sciences Xi’an China University of Chinese Academy of Sciences Beijing China Key Laboratory of Time Reference and Applications Chinese Academy of Sciences Xi’an China

This paper investigates the potential of signals of opportunity for positioning using broadband low Earth orbit constellations. We developed analytical absolute and differential models based on Doppler-shift observations from multi-constellation satellite bursts across various frequency ranges. Owing to the unavailability of multi-constellation broadband receivers, simulations were conducted with the application of two primary restrictions common for these satellites: a 30° elevation mask angle and a 15-s intermittency for observations. Signal attenuation factors were modeled, indicating that free space loss was the dominant factor whereas cloud and fog losses were minimal. The accuracy of absolute static positioning, considering the aforementioned broadband restrictions, reached 4.32 m. The kinematic receiver showed similar trends, with a degraded accuracy of 4.83 m. Tests in urban areas revealed significant accuracy degradation to approximately 10 m. However, the differential model significantly improved kinematic positioning accuracy, achieving promising sub-meter levels even with a limited number of satellites. © 2025 Institute of Navigation.

关键词： Global positioning system

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Precise spectroscopy of metastable Li+using the optical Ramsey technique in support of time dilation tests

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Photonics Research 2025年第1期13卷 201-209页

作者： PENG-PENG ZHOU SHAO-LONG CHEN CHENG-GANG QIN XU-RUI CHANG ZHI-QIANG ZHOU WEI SUN YAO HUANG KE-LIN GAO HUA GUAN State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Innovation Academy for Precision Measurement Science and TechnologyChinese Academy of SciencesWuhan 430071China Information Engineering University Zhengzhou 450001China Key Laboratory of Time Reference and Applications Chinese Academy of SciencesWuhan 430206China MOE Key Laboratory of Fundamental Physical Quantities Measurement&Hubei Key Laboratory of Gravitation and Quantum Physics PGMF and School of PhysicsHuazhong University of Science and TechnologyWuhan 430074China University of Chinese Academy of Sciences Beijing 100049China Key Laboratory of Green and High-end Utilization of Salt Lake Resources Qinghai Institute of Salt LakesChinese Academy of SciencesXining 810008China Wuhan Institute of Quantum Technology Wuhan 430206China

time dilation constitutes a crucial aspect of Lorentz invariance within special relativity and undergoes constant scrutiny through numerous Ives-Stilwell-type experiments employing the Doppler *** our study,we employed optical Ramsey spectroscopy on a Li^(+)ion beam to enhance the precision of measuring the intrinsic transition frequency 23S1-23P2 to the level of four parts in 1010 with speed of *** findings reconciled an existing 2 MHz disparity between collinear and perpendicular laser ***,in conjunction with previous studies on Li^(+)ion beams traveling at speeds of 0.064c and 0.338c[***.3,861(2007);***.113,120405(2014)],we updated the Robertson-Mansouri-Sexl parameterαto be(-10.0±9.9)×10^(-8)and(-2.9±2.0)×10^(-8),respectively.

关键词： spectroscopy effect Ramsey

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Clock laser noise constraining synchronous comparison of spin-squeezed optical clocks

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Physics Letters, Section A: General, Atomic and Solid State Physics 2025年 552卷

作者： Yu, Deshui Zhang, Shougang Chen, Jingbiao National Time Service Center Chinese Academy of Sciences Xi'an710600 China Key Laboratory of Time Reference and Applications Chinese Academy of Sciences Xi'an710600 China University of Chinese Academy of Sciences Beijing100049 China State Key Laboratory of Photonics and Communications Institute of Quantum Electronics School of Electronics Peking University Beijing100871 China Hefei National Laboratory Hefei230088 China

Spin squeezing has been recognized as a powerful tool to overcome the quantum projection noise limit that is imposed on optical clocks with uncorrelated atoms. Yet, the full potential of spin squeezing remains underutilized in precision measurement, due to the limited Ramsey dark period, which is much shorter than 1 s-level atom-laser and 10 s-level atom-atom coherence times. Here, we numerically study the impact of the clock laser noise on the synchronous comparison of spin-squeezed optical clocks. We restrict ourselves to one-axis twisting and measurement-induced spin squeezing protocols that have recently been demonstrated on optical lattice clocks. The simulation results illustrate that for typical lattice clocks with 103 atoms, the metrological enhancement induced by spin squeezing is only attainable for a dark period of less than 0.1 s using the state-of-the-art clock laser. Therefore, further improvement of the clock laser is necessary to bring spin squeezing into the full play. © 2025 Elsevier B.V.

关键词： Clocks

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Quantum microwave photonic mixer featuring high linearity and dual outputs

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Physical Review Applied 2025年第1期23卷 014078-014078页

作者： Xinghua Li Yifan Guo Xiao Xiang Runai Quan Junjie Xing Ruifang Dong Tao Liu Mingtao Cao Ming Li Key Laboratory of Time Reference and Applications National Time Service Center Chinese Academy of Sciences Xi’an 710600 Shaanxi China School of Astronomy and Space Science University of Chinese Academy of Sciences 100049 Beijing China Hefei National Laboratory Hefei 230088 Anhui China State Key Laboratory on Integrated Optoelectronics Institute of Semiconductors Chinese Academy of Sciences 100083 Beijing China School of Electronic Electrical and Communication Engineering University of Chinese Academy of Sciences 100049 Beijing China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences 100190 Beijing China

Microwave frequency mixing is a fundamental functionality in microwave photonics, playing a crucial role in modern radar and wireless communication systems. Classical microwave photonic mixers require both the radio frequency (rf) signal and the local oscillator to be loaded onto the same optical light source, thereby impeding their capability in the context of distributed microwave systems. Using time-energy–entangled biphotons as the optical carrier, the quantum microwave photonic (QMWP) mixer offers a promising solution for attaining nonlocal mixing and surmounting such limitations. In this paper, we explore two types of QMWP mixer based on the configuration of the intensity modulators: cascade type and parallel type. Both QMWP mixers feature the properties of high linearity and dual outputs, with their spurious-free dynamic ranges being identical to that of the equivalent classical microwave photonic mixer. Specifically, the parallel-type QMWP mixer can nonlocally mix two physically separated rf signals, demonstrating its superiority in distributed microwave and millimeter-wave radar systems. Further, by application of multiphoton frequency-entangled sources as optical carriers, the nonlocal microwave frequency conversion capability endowed by the QMWP mixer can be extended to enhance the performance of multiple-path microwave mixing, which is essential for radar net systems.

关键词： Microwave photonics

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