World's most accurate clock unveiled

Posted by Emma Woollacott

Physicists at the National Institute of Standards and Technology (NIST) have built the world's most accurate clock.

Noting that "aluminum is a better timekeeper than mercury" - thanks, we'll bear that in mind when making appointments - the team based the clock on a single atom of aluminum.

It's accurate to one second in about 3.7 billion years.

The new clock is the second version of NIST's quantum logic clock, so called because it borrows the logical processing used for atoms storing data in experimental quantum computing. The second version is more than twice as precise as the original.

"This paper is a milestone for atomic clocks" for a number of reasons, says NIST postdoctoral researcher James Chou, who developed most of the improvements.

It stomps all over the uselessly vague NIST-F1 cesium fountain clock - the US civilian time standard - which loses a whole second every 100 million years.

But because the international definition of the second is based on the cesium atom, cesium remains the 'ruler' for official timekeeping.

The logic clock is based on a single aluminum ion, trapped by electric fields and vibrating at ultraviolet light frequencies - 100,000 times higher than the microwave frequencies used in NIST-F1.

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.

Aluminum is just one contender for a future international time standard. NIST scientists are working on five different types of experimental optical clocks, each based on different atoms and offering its own advantages.

Optical clocks are already measuring possible changes in the fundamental 'constants' of nature - with important implications for the laws of physics.

Next-generation clocks might lead to new types of gravity sensors for exploring underground natural resources and fundamental studies of the Earth. Other possible applications may include ultra-precise autonomous navigation, such as landing planes by GPS.