Content of SPECIAL TOPIC—Ultracold atom and its application in precision measurement in our journal

Published in last 1 year |  In last 2 years |  In last 3 years |  All Please wait a minute... For selected: Download citations EndNote Ris BibTeX Toggle thumbnails Select Ultradilute self-bound quantum droplets in Bose-Bose mixtures at finite temperature Jia Wang(王佳), Xia-Ji Liu(刘夏姬), and Hui Hu(胡辉) Chin. Phys. B, 2021, 30 (1): 010306.   DOI: 10.1088/1674-1056/abd2ad Abstract （602）   HTML （3）    PDF （819KB）（134）       Knowledge map    We theoretically investigate the finite-temperature structure and collective excitations of a self-bound ultradilute Bose droplet in a flat space realized in a binary Bose mixture with attractive inter-species interactions on the verge of mean-field collapse. As the droplet formation relies critically on the repulsive force provided by Lee-Huang-Yang quantum fluctuations, which can be easily compensated by thermal fluctuations, we find a significant temperature effect in the density distribution and collective excitation spectrum of the Bose droplet. A finite-temperature phase diagram as a function of the number of particles is determined. We show that the critical number of particles at the droplet-to-gas transition increases dramatically with increasing temperature. Towards the bulk threshold temperature for thermally destabilizing an infinitely large droplet, we find that the excitation-forbidden, self-evaporation region in the excitation spectrum, predicted earlier by Petrov using a zero-temperature theory, shrinks and eventually disappears. All the collective excitations, including both surface modes and compressional bulk modes, become softened at the droplet-to-gas transition. The predicted temperature effects of a self-bound Bose droplet in this work could be difficult to measure experimentally due to the lack of efficient thermometry at low temperatures. However, these effects may already present in the current cold-atom experiments. Select Theoretical study of the hyperfine interaction constants, Landé g-factors, and electric quadrupole moments for the low-lying states of the 61Niq+ ( q=11, 12, 14 , and 15) ions Ting-Xian Zhang(张婷贤), Yong-Hui Zhang(张永慧), Cheng-Bin Li(李承斌), and Ting-Yun Shi(史庭云) Chin. Phys. B, 2021, 30 (1): 013101.   DOI: 10.1088/1674-1056/abc7a3 Abstract （389）   HTML （2）    PDF （645KB）（184）       Knowledge map    Highly charged nickel ions have been suggested as candidates for the ultra-precise optical clock, meanwhile the relevant experiment has been carried out. In the framework of the multiconfiguration Dirac-Hartree-Fock (MCDHF) method, we calculated the hyperfine interaction constants, the Landé g-factors, and the electric quadrupole moments for the low-lying states in the 61Ni11+, 61Ni12+, 61Ni14+, and 61Ni15+ ions. These states are clock states of the selected clock transitions in highly charged nickel ions (see Fig. \fref1 1). Based on discussing the effects of the electron correlations, the Breit interaction, and quantum electrodynamics (QED) effect on these physical quantities, reasonable uncertainties were obtained for our calculated results. In addition, the electric quadrupole frequency shifts and the Zeeman frequency shifts of the clock transitions concerned were analyzed. Select Study of optical clocks based on ultracold 171Yb atoms Di Ai(艾迪), Hao Qiao(谯皓), Shuang Zhang(张爽), Li-Meng Luo(骆莉梦), Chang-Yue Sun(孙常越), Sheng Zhang(张胜), Cheng-Quan Peng(彭成权), Qi-Chao Qi(齐启超), Tao-Yun Jin(金涛韫), Min Zhou(周敏), Xin-Ye Xu(徐信业) Chin. Phys. B, 2020, 29 (9): 090601.   DOI: 10.1088/1674-1056/aba099 Abstract （1043）   HTML    PDF （3113KB）（308）       Knowledge map    The optical atomic clocks have the potential to transform global timekeeping, relying on the state-of-the-art accuracy and stability, and greatly improve the measurement precision for a wide range of scientific and technological applications. Herein we report on the development of the optical clock based on 171Yb atoms confined in an optical lattice. A minimum width of 1.92-Hz Rabi spectra has been obtained with a new 578-nm clock interrogation laser. The in-loop fractional instability of the 171Yb clock reaches 9.1×10-18 after an averaging over a time of 2.0×104 s. By synchronous comparison between two clocks, we demonstrate that our 171Yb optical lattice clock achieves a fractional instability of 4.60×10-16/√τ. Select Calibration of a compact absolute atomic gravimeter Hong-Tai Xie(谢宏泰), Bin Chen(陈斌), Jin-Bao Long(龙金宝), Chun Xue(薛春), Luo-Kan Chen(陈泺侃), Shuai Chen(陈帅) Chin. Phys. B, 2020, 29 (9): 093701.   DOI: 10.1088/1674-1056/aba27b Abstract （946）   HTML    PDF （702KB）（246）       Knowledge map    Compact atomic gravimeters are the potential next generation precision instruments for gravity survey from fundamental research to broad field applications. We report the calibration results of our home build compact absolute atomic gravimeter USTC-AG02 at Changping Campus, the National Institute of Metrology (NIM), China in January 2019. The sensitivity of the atomic gravimeter reaches 35.5 μGal/√Hz (1 μGal=1×10-8 m/s2) and its long-term stability reaches 0.8 μGal for averaging over 4000 seconds. Considering the statistical uncertainty, the dominant instrumental systematic errors and environmental effects are evaluated and corrected within a total uncertainty (2σ) of 15.3 μGal. After compared with the reference g value given by the corner cube gravimeter NIM-3A, the atomic gravimeter USTC-AG02 reaches the degree of equivalence of 3.7 μGal. Select Suppression of Coriolis error in weak equivalence principle test using 85Rb-87Rb dual-species atom interferometer Wei-Tao Duan(段维涛), Chuan He(何川), Si-Tong Yan(闫思彤), Yu-Hang Ji(冀宇航), Lin Zhou(周林), Xi Chen(陈曦), Jin Wang(王谨), Ming-Sheng Zhan(詹明生) Chin. Phys. B, 2020, 29 (7): 070305.   DOI: 10.1088/1674-1056/ab969a Abstract （535）   HTML    PDF （746KB）（141）       Knowledge map    Coriolis effect is an important error source in the weak equivalence principle (WEP) test using atom interferometer. In this paper, the problem of Coriolis error in WEP test is studied theoretically and experimentally. In theoretical simulation, the Coriolis effect is analyzed by establishing an error model. The measurement errors of Eötvös coefficient (η) in WEP test related to experimental parameters, such as horizontal-velocity difference and horizontal-position difference of atomic clouds, horizontal-position difference of detectors, and rotation compensation of Raman laser's mirror are calculated. In experimental investigation, the position difference between 85Rb and 87Rb atomic clouds is reduced to 0.1 mm by optimizing the experimental parameters, an alternating detection method is used to suppress the error caused by detection position difference, thus the Coriolis error related to the atomic clouds and detectors is reduced to 1.1×10-9. This Coriolis error is further corrected by compensating the rotation of Raman laser's mirror, and the total uncertainty of η measurement related to the Coriolis effect is reduced as δη=4.4×10 -11. Select Michelson laser interferometer-based vibration noise contribution measurement method for cold atom interferometry gravimeter Ning Zhang(张宁), Qingqing Hu(胡青青), Qian Wang(王倩), Qingchen Ji(姬清晨), Weijing Zhao(赵伟靖), Rong Wei(魏荣), Yuzhu Wang(王育竹) Chin. Phys. B, 2020, 29 (7): 070601.   DOI: 10.1088/1674-1056/ab8885 Abstract （586）   HTML    PDF （2010KB）（204）       Knowledge map    The measurement performance of the atom interferometry absolute gravimeter is strongly affected by the ground vibration noise. We propose a vibration noise evaluation scheme using a Michelson laser interferometer constructed by the intrinsic Raman laser of the atomic gravimeter. Theoretical analysis shows that the vibration phase measurement accuracy is better than 4 mrad, which corresponds to about 10-10 g accuracy for a single shot gravity measurement. Compared with the commercial seismometer or accelerometer, this method is a simple, low cost, direct, and fully synchronized measurement of the vibration phase which should benefit the development of the atomic gravimeter. On the other side, limited by equivalence principle, the result of the laser interferometer is not absolute but relative vibration measurement. Triangular cap method could be used to evaluation the noise contribution of vibration, which is a different method from others and should benefit the development of the atomic gravimeter. Select A transportable optical lattice clock at the National Time Service Center De-Huan Kong(孔德欢), Zhi-Hui Wang(王志辉), Feng Guo(郭峰), Qiang Zhang(张强), Xiao-Tong Lu(卢晓同), Ye-Bing Wang(王叶兵), Hong Chang(常宏) Chin. Phys. B, 2020, 29 (7): 070602.   DOI: 10.1088/1674-1056/ab9290 Abstract （718）   HTML    PDF （2701KB）（307）       Knowledge map    We report a transportable one-dimensional optical lattice clock based on 87Sr at the National Time Service Center. The transportable apparatus consists of a compact vacuum system and compact optical subsystems. The vacuum system with a size of 90 cm×20 cm×42 cm and the beam distributors are assembled on a double-layer optical breadboard. The modularized optical subsystems are integrated on independent optical breadboards. By using a 230 ms clock laser pulse, spin-polarized spectroscopy with a linewidth of 4.8 Hz is obtained which is close to the 3.9 Hz Fourier-limit linewidth. The time interleaved self-comparison frequency instability is determined to be 6.3×10-17 at an averaging time of 2000 s.