Research on the optical time scale based on an optical clock with the single 40Ca+ion
Optical atomic clocks have been improved greatly in recent years.The Consultative Committee for Time and Frequency(CCTF)proposes the redefinition of the second in the International System of Units SI based on the optical clocks by 2030.The technology plans and practical steps are discussed.Therefore,the development of optical time scales with optical clocks and microwave clocks is the leading research topic at home and abroad.By an optical clock with a single 40Ca+ion(TOC-729)steering a microwave clock H,we study the optical time scale TS(Ca+).The uptime of this TOC-729 is 87％over 7 months,and the frequency instability is 8E-17/day expressed by the Allan deviation.There are two measurement methods of the optical clock TOC-729 relative to the microwave clock H,namely locking an optical frequency to a microwave clock frequency(the up-converting method)and conversion of an optical clock frequency into the RF range(the down-converting method).The up-converting method amplifies noises from the microwave clock H.The frequency instability of measurement data is inferior to the microwave clock H.For the down-converting method,the frequency instability of measurement data is almost the same as the micro wave clock H,showing that the optical clock can accurately measure the micro wave clock H with this method.The free-running H clock is compared with the signal down-converted from TOC-729 by recording the phase difference,and the frequency offset in H clock frequency is corrected by a phase micro stepper.The optical time scale(Ca+)is independent,which steering to UTC is 0.6ns in a month.The research is significant to establish and maintain the international time scale TAI with highly stable optical standards redefining the second,and the work can also improve and develop the national time scales in China.
optical clock with a single 40Ca+ionan optical time scalethe up-converting methodthe down-converting methodan optical clock steering a microwave clock
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维普
