Long-Lifetime Optical Trapping of a ^(40)Ca^(+) Ion

We have experimentally achieved the all-optical trapping of a ^(40)Ca^(+)ion.An optical dipole trap was established using a high-power,far-detuned,tightly focused laser with a wavelength of 532 nm.The single ^(40)Ca^(+)ion was trapped without any RF fields and demonstrated a long lifetime of over 3 s.In this experiment,we implemented several measures to improve the optical trapping probability,including focusing the dipole beam waist near the diffraction limit,precisely compensating for stray electric fields,and mitigating electron shelving in metastable states.The optical trapping of a ^(40)Ca^(+)ion eliminates the influence of micromotion induced by RF fields,potentially paving the way for development of all-optical trapping ion optical clocks.

Progress on the^40Ca^+ion optical clock

Progress of the ^40Ca^+ion optical clock based on the 4^2S1/2-3d ^2D5/2 electric quadrupole transition is reported.By setting the drive frequency to the“magic”frequencyΩ0,the frequency uncertainty caused by the scalar Stark shift and second-order Doppler shift induced by micromotion is reduced to the 10^-19 level.By precisely measuring the differential static scalar polarizability∆α0,the uncertainty due to the blackbody radiation(BBR)shift(coefficient)is reduced to the 10^-19 level.With the help of a second-order integrating servo algorithm,the uncertainty due to the servo error is reduced to the 10^-18 level.The total fractional uncertainty of the ^40Ca^+ion optical clock is then improved to 2.2×10^-17,whereas this value is mainly restricted by the uncertainty of the BBR shift due to temperature fluctuations.The state preparation is introduced together with improvements in the pulse sequence,and furthermore,a better signal to noise ratio(SNR)and less dead time are achieved.The clock stability of a single clock is improved to 4.8×10^-15√τ(in seconds).

Reducing statistical noise in frequency ratio measurement between Ca+and Sr optical clocks with a frequency-synthesized local oscillator from a Sr optical clock

Optical frequency ratio measurement between optical atomic clocks is essential to precision measurement as well as the redefinition of the second.Currently,the statistical noise in frequency ratio measurement of most ion clocks is limited by the frequency instability of ion clocks.In this work,we reduce the statistical noise in the frequency ratio measurement between a transportable Ca^(+)optical clock and a Sr optical lattice clock down to 2.2×10^(-15)∕√τp.The local oscillator of the Ca^(+)optical clock is frequency-synthesized from the Sr optical lattice clock,enabling a longer probe time for Ca^(+)clock transition.Compared to previous measurement using independent local oscillators,we achieve 10-fold reduction in comparison campaign duration.