Trapping of a single Ca+ ion for its use as a frequency standard

Lijin Wu, Ting-Yun Shi, Kelin Gao

The source of systematic frequency shift of single-ion optical frequency standard of 40 Ca + ion trapped in endcap trap and laser-cooled to a few of mK is analysed and calculated. Second-order Doppler shift, Stark shift due to micromotion and thermal motion, blackbody Stark shift and ac Stark shift are calculated for the ground state and excited 3 d 2 D 5/2 state. The Hertz-level measurement of the optical clock frequency in a single 40 Ca + ion can be performed.

Liam Lewis, T. E. Smith, Samuel R. Stein

P. E. Toschek, Bernd Appasamy, Ph. W. Courteille +2 more

Kouki Matsubara, Y. Li, Masatoshi Kajita +3 more

Abstract —We are proceeding with a development of an optical frequency standard using a 2 S 1/2 – 2 D 5/2 electric quadrupole transition of Ca + ions in a small radio-frequency trap. We have theoretically confirmed that an uncertainty of <1 x 10 -15 is attainable in measurement of the 2 S 1/2 – 2 D 5/2 transition frequency. Experimentally, we have developed stable laser-diode systems and observed the quantum jump of single 40 Ca + ions to the 2 D 5/2 state. I. I NTRODUCTION The uncertainty of primary frequency standards using Cs atoms reaches around 10 -15 and the inherent limits involved in them are discussed. On the other hand, frequency standards using new materials and methods are proposed for developing more accurate frequency standards. Recently, several groups have measured frequencies of the ionic forbidden transitions in the optical region to apply them to the clock transitions of optical frequency standards [1]. We now proceeds with study on an optical frequency standard using single Ca

Hua Guan, 高克林, Yao HUANG

The experimental study at Wuhan Institute of Physics and Mathematics (WIPM), Chinese Academy of Scienses (CAS) on the precision spetroscopy based on single trapped Ca+ ion is described in this paper. A single Ca+ ion is trapped in a miniature Paul trap and laser cooled to Lamb-Dicke regime, and the ion can be trapped more than 2 months. The linewidth of the 729 nm laser for probing the Ca+ 4s2S1/2-3d2D5/2 clock transition is reduced to lessthan 1 Hz by locked to a super cavity, and the 729 nm laser can be locked more than 1 month continuously. Two similar Ca + ion optical frequency standards are set up for frequency comparison. The systematic uncertainty is evaluated to be <6 ´ 10−17 for both ftrquency standards. The frequency difference of two frequency standards is measured to be 3.0 (5.5) ´ 10−17 within 42 d. The Allan deviation for a single clock is measured to be 1×10−14τ−1/2 with a 3-d-continuous comparison, the stability for a reaches 7 ´ 10−17 at an averaging time of 20000 s. Meanwhile, the absolute frequency of the Ca+ 4s2S1/2-3d2D5/2 clock transition is measured to be 411042129776401.7(1.1) Hz with respect to the SI second through the Global Positioning System (GPSx). The precision spectroscopy experiments are carried out based on the single Ca+ ion system. The magic wavelengths for the Ca+ optical frequency standardare measured to be λ|mj|=1/2=395.7992(7) nm and λ|mj|=3/2=395.7990(7) nm, which agrees with theoretical calculation made by Tang et al. The lifetime of the 3d2D5/2 is measured to be 1174(10) ms, which is agree with the experimental measurement made by University of Oxford and University of Innsbruck and the recent theoretical calculation made by Sahoo.

HERBERT WALTHER