Investigation of cold atom collision frequency shift measured by rapid adiabatic passage in cesium fountain clock

doi:10.7498/aps.69.20191800

NTSC-IR

	Investigation of cold atom collision frequency shift measured by rapid adiabatic passage in cesium fountain clock
	Guan Yong 1,2,3; Liu Dan-Dan 1,2,3; Wang Xin-Liang 1,2,3; Zhang Hui 1,2,3; Shi Jun-Ru 1,2,3; Bai Yang 1,2,3; Ruan Jun1,2 ; Zhang Shou-Gang 1,2
	2020-07-20
发表期刊	ACTA PHYSICA SINICA
ISSN	1000-3290
卷号	69 期号:14 页码:8
摘要	Cold collision frequency shift is one of the major systematic effects which limit the frequency uncertainty of the cesium fountain atomic clock. It is proportional to the effective atomic density, which is defined as the average density over the initial spacial and velocity distribution. The measurement of the frequency shift is based on a differential method, in which the fountain clock is operated with two different atomic densities, i.e. high density and low density, in turn. The clock frequency without collision shift can be achieved by linear extrapolation with the frequencies and density ratios of two states. For the density ratio is estimated with the atom number, it plays a crucial role in generating atoms with same density distribution for reducing systematic uncertainty in cold collision frequency shift estimation. The rapid adiabatic passage method is used in Cesium fountain clock to realize homogeneous transition probability, which modulates the amplitude and frequency of microwave continuously to prepare atom sample. To investigate the precision of this method, theoretical analysis and experimental measurement are both used here. An equation of deviation is derived from the time evolution of Bloch vector. The vector rotates at angular speed Omega with the rotation axis processing at lower angular speed. The deviations in the two directions on the surface of Bloch sphere are determined by the equations which are similar to wave equations, and can be simplified into wave equations when the deviations are sufficiently small. It is shown in the equations that the deviations are stimulated by angular velocity and angular acceleration of the precession, and is inversely proportional to the square of Omega. Further calculation shows that the deviation becomes smaller when the amplitude of microwave frequency and Rabi frequency are close to each other. It is then confirmed experimentally. The effects of some other parameters, such as the pulse length and time delay, on transition probability are also measured, showing that the RAP method is insensitive to these parameters up to a large scope. The precision of RAP method is dominated by three factors. The first factor is the product of rotating angular speed Omega and pulse length T, i.e. Omega T: The increase of Omega T can reduce the uncertainty to a satisfactory degree. The second factor is the uncertainty of resonant frequency, so the measurement is required to be precise. The third factor is the unexpected atoms which are not selected by the microwave, and may be attributed to pulling light. After optimizing the parameters, the ratio of low density to high density can approach to 0.5 with 3 x 10(-3) uncertainty, which leads to a systematic relative uncertainty of cold collision shift up to 1.6 x 10(-16).
关键词	cesium fountain atomic clock cold collision frequency shift rapid adiabatic passage method
资助者	National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China
DOI	10.7498/aps.69.20191800
关键词[WOS]	DISTRIBUTED CAVITY PHASE ; ACCURACY EVALUATION
语种	英语
资助项目	National Key Research and Development Program of China[2016YFF0200202]
资助者	National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China ; National Key Research and Development Program of China
WOS研究方向	Physics
WOS类目	Physics, Multidisciplinary
WOS记录号	WOS:000560751300007
出版者	CHINESE PHYSICAL SOC
引用统计
文献类型	期刊论文
条目标识符	http://210.72.145.45/handle/361003/9402
专题	中国科学院国家授时中心
通讯作者	Ruan Jun
作者单位	1.Chinese Acad Sci, Natl Time Serv Ctr, Xian 710600, Peoples R China 2.Chinese Acad Sci, Natl Time Serv Ctr, Key Lab Time & Frequency Primary Stand, Xian 710600, Peoples R China 3.Univ Chinese Acad Sci, Beijing 100049, Peoples R China
推荐引用方式 GB/T 7714	Guan Yong,Liu Dan-Dan,Wang Xin-Liang,et al. Investigation of cold atom collision frequency shift measured by rapid adiabatic passage in cesium fountain clock[J]. ACTA PHYSICA SINICA,2020,69(14):8.
APA	Guan Yong.,Liu Dan-Dan.,Wang Xin-Liang.,Zhang Hui.,Shi Jun-Ru.,...&Zhang Shou-Gang.(2020).Investigation of cold atom collision frequency shift measured by rapid adiabatic passage in cesium fountain clock.ACTA PHYSICA SINICA,69(14),8.
MLA	Guan Yong,et al."Investigation of cold atom collision frequency shift measured by rapid adiabatic passage in cesium fountain clock".ACTA PHYSICA SINICA 69.14(2020):8.