A strontium clock that loses one second every 200 million years

An atomic clock that is based on thousands of strontium atoms trapped using lasers and loses only 1 second in more than 200 million years has been demonstrated by researchers at the Joint Institute for Laboratory Astrophysics, a collaboration between the US National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder. It is more precise than the current US time standard, which is based on a "fountain" of cesium atoms and accurate to 1 second in 80 million years.

Super-precise atomic clocks are used to synchronize global telecommunications networks and deep-space communications, as well as military navigation and positioning.

The new clock uses lasers to trap thousands of ultra cold strontium atoms in an optical lattice. The strontium atoms absorb very precise frequencies of optical light. This allows researchers to use them to keep time. (A strontium clock such as the one demonstrated ticks 430 million times each second.) The NIST standard uses microwaves, which have lower frequencies (and hence lower precision).

However, the strontium clock is the not the world's most precise. That honor goes to an experimental design based on a single mercury ion. It is supposedly so accurate that it loses only 1 second in 400 million years.

But strontium-based clocks have some advantages, according to scientists.

"A large ensemble of neutral atoms offers an enhanced clock signal strength that will make them more precise than a single trapped ion based clock," said Jun Ye, who is the leader of the scientific team that developed the new strontium clock.

So what is next?

"We will continue to enhance the clock precison and the clock accuracy," said Ye. "At this point, it's likely that the performance improvement by another factor of 10 will come relatively quickly."

For more information, go to the Jun Ye's research page on strontium clocks: http://jilawww.colorado.edu/yelabs/research/ultracold.html#jumpToClock


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