Frequency ratio of an In ion clock and a Sr optical lattice clock.

We report on the first, to the best of our knowledge, frequency ratio measurement of an singleion clock and a optical lattice clock. A hydrogen maser serves as a flywheel oscillator to measure the ratio by independent optical combs. From 89,000 s of measurement time, the frequency ratio / is determined to be 2.

Frequency measurement of the clock transition of an indium ion sympathetically-cooled in a linear trap.

We report frequency measurement of the clock transition in an In ion sympathetically-cooled with Ca ions in a linear rf trap. The Ca ions are used as a probe of the external electromagnetic field and as the coolant for preparing the cold In. The frequency is determined to be 1 267 402 452 901 049.

Direct comparison of a Ca+ single-ion clock against a Sr lattice clock to verify the absolute frequency measurement.

Optical frequency comparison of the (40)Ca(+) clock transition ν(Ca)((2)S(1/2-)(2D(5/2), 729 nm) against the (87)Sr optical lattice clock transition ν(Sr) ((1)S(0)-(3)P(0), 698 nm) has resulted in a frequency ratio ν(Ca) / ν(Sr) = 0.957 631 202 358 049 9(2 3). The rapid nature of optical comparison allowed the statistical uncertainty of frequency ratio ν(Ca) / ν(Sr) to reach 1 × 10(-15) in 1000s and yielded a value consistent with that calculated from separate absolute frequency measurements of ν(Ca) using the International Atomic Time (TAI) link.