New atomic clock is world's most accurate

Scientists claim to have developed a new record-breaking atomic clock that is so precise it neither loses nor gains a second in five billion years - longer than the age of the Earth.
The 'strontium lattice clock' is 50 per cent more accurate than the previous record holder, the National Institute of Standards and Technology (NIST) quantum logic clock.
A research group led by a NIST physicist unveiled the experimental strontium atomic clock that has set new world records for both precision and stability - key metrics for the performance of a clock.
Precision refers to how closely the clock approaches the true resonant frequency at which its reference atoms oscillate between two electronic energy levels.

The new strontium clock is so precise it would neither gain nor lose one second in about 5 billion years, if it could operate that long, researchers said.
This time period is longer than the age of Earth, an estimated 4.5 billion years old, researchers said.

The strontium clock's stability - the extent to which each tick matches the duration of every other tick - is about the same as NIST's ytterbium atomic clock.
Stability determines in part how long an atomic clock must run to achieve its best performance through continual averaging, researchers said.
The strontium and ytterbium lattice clocks are so stable that in just a few seconds of averaging they outperform other types of atomic clocks that have been averaged for hours or days.

"We already have plans to push the performance even more," NIST/JILA Fellow and group leader Jun Ye said.
The current international definition of units of time requires the use of cesium-based atomic clocks, such as the current US civilian time standard clock, the NIST-F1 cesium fountain clock, researchers said.
Hence only cesium clocks are accurate by definition, even though the strontium clock has better precision. The strontium lattice clock and some other experimental clocks operate at optical frequencies, much higher than the microwave frequencies used in cesium clocks.
Thanks to the work at NIST, JILA and other research organisations across the world, the strontium lattice clock and other experimental clocks may someday be chosen as new timekeeping standards by the international community, researchers said.

The clock was described in a paper in Journal Nature.