A transportable optical clock refer to the 4s 2 S 1/2 -3d 2 D 5/2 electric quadrupole transition at 729 nm of single 40 Ca + trapped in mini Paul trap has been developed. The physical system of 40 Ca + optical clock is re-engineered from a bulky and complex setup to an integration of two subsystems: a compact single ion unit including ion trapping and detection modules, and a compact laser unit including laser sources, beam distributor and frequency reference modules. Apart from the electronics, the whole equipment has been constructed within a volume of 0.54 m 3 . The systematic fractional uncertainty has been evaluated to be 7.7×10 -17 , and the Allan deviation fits to be 14 2.3 10    by clock self-comparison with a probe pulse time 20 ms.

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The 27Al+ ion optical clock is one of the most attractive optical clocks due to its own advantages such as low black-body radiation shift at room temperature and insensitivity to the magnetic drift. However, it cannot be laser-cooled directly in the absence of 167nm laser to date. This problem can be solved by sympathetic cooling. In this work, a linear Paul trap is used to trap both 40Ca+ and 27 Al+ ions simultaneously, and a single Doppler-cooled40 Ca+ ion is employed to sympathetically cool a single 27Al+ ion. Thus a ‘bright-dark’ two-ion crystal has been successfully synthesized. The temperature of the crystal has been estimated to be about 7 mK by measuring the ratio of carrier and sideband spectral intensities. Finally, the dark ion is proved to be an 27Al+ ion by precise measuring of the ion crystal's secular motion frequency, which means that it is a great step for our 27Al+ quantum logic clock.