Vortrag

We present our recent results in developing an optical-lattice clock based on the ¹S₀-³P₀ transition in neutral ⁸⁷Sr. The combination of the tight confinement provided by the optical lattice, and the sub-Hz linewidth of a high stability diode laser system, has allowed observation of resonances with line quality factors exceeding 2x10¹⁴. Aided mainly by this high line Q, we have experimentally constrained the total systematic uncertainty of our lattice clock (including AC stark, magnetic, and collision shifts) to 9x10^–16, a level which is approaching that of current Cs-fountains. The absolute frequency of the clock transition is found to be 429,228,004,229,874.0(1.1) Hz, where the 2.5x10^–15 uncertainty is mainly due to the maser and transfer system employed. This value agrees well with our previous measurements as well as with recent high accuracy measurements from groups in Paris and Tokyo. Using resolved nuclear-spin sublevels, we have also performed a precision measurement of the hyperfine-induced differential g-factor of the clock states.

To prepare for future high-stability remote synchronization and intercomparisons of high accuracy optical atomic clocks, we have recently demonstrated transfer of an optical frequency standard over a ~7 km fiber link with instability of 10^–17 at 1 s, averaging down to 10^–19 at 10000 s.