The Research Of Sympathetic And Sideband Cooling Of⁴⁰Ca⁺-²⁷Al⁺ Ion Pair

With the development of sympathetic cooling,sideband cooling,and quantum logic spec-troscopy,more and more ion species become the candidates for frequency standards,such as 115In+,27 Al+ and so on.The clock transition of 27 At is 1So-3P0,which has a high Q factor of 2 x 1017,suffers no electric quadrupole shifts,and has linear and quadratic Zeeman shifts of a few 10 kHz/mT and 10 Hz/mT2,respectively.What's more,27Al+ has the smallest sensitivity to blackbody radiation among those candidates.Lacking of relevant technology,the laser of 167 nm for the ion's Doppler cooling and frequency measurement is difficult to be achieved,sympathetic cooling together with quantum logic spectroscopy solves the problems properly.In the year of 2010,National Institute of Standard and Technology(NIST)realized the frequency comparison between two 27Al+ optical clocks,which has a fractional frequency inaccuracy of 8.6 × 10-18.The logic ions in those two clocks they chose were 9Be+ and 25Mg+,respectively.40Ca+was chosen as logic one instead in our lab for the 40Ca+ has a simple energy structure and all the radiations needed could be obtained from diode lasers.We have realized the trap of 40Ca+-27Al+ ion pair and the sideband cooling of 40Ca+.In addition,the ion pair was cooled to ground state.The main content is categorized as follows:1.The establishment of the experimental platform.It consists of linear Paul trap,ultra-high vacuum system,helical resonator,and soon.2.The vibration and zero-crossing temperature of cavity are simulated using finite elet-ment analysis(FEA)method,one FP cavity with low vibration sensitivity and zero-crossing temperature tuning is designed.One 729 nm ultranarrow laser system is established,and the laser linewidth is measured by beating with another laser to be about 1 Hz.3.One 40Ca+ is trapped with linear Paul trap and Doppler cooled in vacuum system.It could be trapped longer than 5 days without Doppler cooling.4.A single dark ion is trapped and sympathetically cooled by a Doppler-cooled 40Ca+ ion.The number of dark ion is confirmed by ions distance and the dark ion is proved to be 27 Al+with measuring frequency of secular motion precisely.5.One 40Ca+ is cooled to vibrational ground state by sideband cooling.It's mean vibra-tional quantum number is 0.05 and the ion is in the ground state with a percent of 95.2%..6.The axial COM and BM of 40Ca+-27Al+ ion pair is cooled to vibration ground state by sideband cooling with mean vibration quanta of 0.12 and 0.04 respectively.