Scientists build world's most accurate clock

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Washington: Scientists claim to have developed the world's most precise clock made from the element ytterbium, whose ticking rate varies less than two parts in one quintillion - ten times better than any other device.
A pair of experimental atomic clocks based on ytterbium atoms has set a new record for stability, researchers said.
The clocks act like 21st-century pendulums or metronomes that could swing back and forth with perfect timing for a period comparable to the age of the universe. Physicists at the National Institute of Standards and Technology (NIST) report in the journal Science Express that the ytterbium clocks' tick is more stable than any other atomic clock.
Stability can be thought of as how precisely the duration of each tick matches every other tick. The ytterbium clock ticks are stable to within less than two parts in 1 quintillion (1 followed by 18 zeros), roughly 10 times better than the previous best published results for other atomic clocks, researchers said.
This dramatic breakthrough has the potential for significant impacts not only on timekeeping, but also on a broad range of sensors measuring quantities that have tiny effects on the ticking rate of atomic clocks, including gravity, magnetic fields, and temperature.
It is a major step in the evolution of next-generation atomic clocks under development worldwide, researchers said.
"The stability of the ytterbium lattice clocks opens the door to a number of exciting practical applications of high-performance timekeeping," co-author Andrew Ludlow said.
Each of NIST's ytterbium clocks relies on about 10,000 rare-earth atoms cooled to 10 microkelvin (10 millionths of a degree above absolute zero) and trapped in an optical lattice—a series of pancake-shaped wells made of laser light.
Another laser that 'ticks' 518 trillion times per second provokes a transition between two energy levels in the atoms. The large number of atoms is key to the clocks' high stability, said researchers.
The ticks of any atomic clock must be averaged for some period to provide the best results. One key benefit of the very high stability of the ytterbium clocks is that precise results can be achieved very quickly, they said.
For example, the current US civilian time standard, the NIST-F1 cesium fountain clock, must be averaged for about 400,000 seconds (about five days) to achieve its best performance. The new ytterbium clocks achieve that same result in about one second of averaging time.
Given this high level of stability the ytterbium clocks can make measurements extremely rapidly—in real time in many cases - which could be important in rapidly changing application settings, such as the factory floor and the natural environment.