Precision Time Ultra-Precise Quantum-Logic Clock

Physicists at the National Institute of Standards and Technology (NIST) have built an enhanced version of an experimental atomic clock based on a single aluminum atom that is now the world's most precise clock, more than twice as precise as the previous pacesetter based on a mercury atom. The new aluminum clock would neither gain, nor lose, one second in about 3.7 billion years.

The new clock is the second version of NIST's “quantum logic clock,” which borrows the logical processing used for atoms storing data in experimental quantum computing. The second version offers more than twice the precision of the original and is widening its lead over the NIST-F1 cesium fountain clock, the U.S. civilian time standard, which currently keeps time to within 1 second in about 100 million years.

Because the international definition of the second is based on the cesium atom, cesium remains the “ruler” for official timekeeping, and no clock can be more accurate than cesium-based standards.

The logic clock is based on a single aluminum ion trapped by electric fields and vibrating at ultraviolet light frequencies, which are 100,000 times higher than microwave frequencies used in cesium clocks. Optical clocks thus divide time into smaller units, and could someday lead to time standards more than 100 times as accurate as today's microwave standards. Higher frequency is one of a variety of factors that enables improved precision and accuracy.

NIST scientists are working on five different types of experimental optical clocks, each based on different atoms and offering its own advantages. NIST's construction of a second, independent version of the logic clock proves it can be replicated, making it one of the first optical clocks to achieve that distinction.
Any future time standard will need to be reproduced in many laboratories. 
The second version of the logic clock offers more than twice the precision of the original.

For more information visit www.nist.gov/pml/div688/logicclock_020410.cfm.