Collaboration helps make JILA strontium atomic clock 'best in class'

'Crystal of light' clock surpasses accuracy of NIST-F1 fountain clock

JILA's strontium atomic clock is now the world's most accurate clock based on neutral atoms. Click here for more information.

BOULDER, Colo.- A next-generation atomic clock that tops previous records for accuracy in clocks based on neutral atoms has been demonstrated by physicists at JILA, a joint institute of the Commerce Department's National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder. The new clock, based on thousands of strontium atoms trapped in grids of laser light, surpasses the accuracy of the current U.S. time standard based on a "fountain" of cesium atoms.

JILA's experimental strontium clock, described in the Feb. 14 issue of Science Express,* is now the world's most accurate atomic clock based on neutral atoms, more than twice as accurate as the NIST-F1 standard cesium clock located just down the road at the NIST campus in Boulder.

The JILA strontium clock would neither gain nor lose a second in more than 200 million years, compared to NIST F-1's current accuracy of over 80 million years.

The advance was made possible by Boulder's critical mass of state-of-the-art timekeeping equipment and expertise. The JILA strontium clock was evaluated by remotely comparing it to a third NIST atomic clock, an experimental model based on neutral calcium atoms. The best clocks can be precisely evaluated by comparing them to other nearby clocks with similar performance; very long-distance signal transfer, such as by satellite, is too unstable for practical, reliable comparisons of the new generation of clocks. In the latest experiment, signals from the two clocks were compared via a 3.5-kilometer underground fiber-optic cable.