The Realization And Systematic Uncertainty Of Quantum Logic Optical Frequency Standard Using⁴⁰Ca⁺-²⁷Al⁺ Ion Pair

In recent years,the stability and uncertainty of optical clocks have surpassed those of cesium time standard,which triggers a discussion about a possible redefinition of the SI second.The quality factor of the 1S0-3P0 clock transition of 27Al+ ion is as high as 2 X 1017,and the natural linewidth is only 8 mHz.It is insensitive to the jitter of electric fields and magnetic fields,which will cause extremely low frequency shift uncertainty caused by electric quadrupole effect,Zeeman effect,and blackbody radiation.People have been considering it as a strong candidate in optical frequency research for a long time.In this paper,the realization of the closed-loop of the clock transition spectrum of 27Al+ and systematic uncertainty using the 40Ca+ ion as the auxiliary ion for the sympathetic cooling and quantum logic spectrum.The main results are summarized as follows:1.Designed and developed a new physical system for the 40Ca+-27Al+ion pair.The structure of the ion trap increases the RF drive frequency and improves ion stability.At the same time,servo feedback is used to stabilize the RF power to reduce the measurement error of the macro motion frequency.Besides,the new design of the vacuum system can increase the degree of vacuum,so the life of the trapped 27Al+ ion can exceed 1 hour.2.For the first time,S1/2(mf=-1/2)?D5/2(mf=-1/2)transition is used in the quantum logic scheme.Considering the low magnetic sensitivity,combined with magnetic compensation,the coherence time of the system reaches 1ms.3.Using the quantum logic scheme,by optimizing the quantum nondemolition measurement sequence,a clock tranaitsion sepctrum with 30Hz linewidth is obtained.4.The closed-loop operation of the clock transition spectrum was realized.The experimental parameters of this system were used to evaluate the main influencing factors affecting the systematic uncertainty,reaching 8.5×10-18.