Physicists at the U.S. National Institute of Standards and Technology (NIST) claim to have created a pair of the world's most precise atomic timekeepers made from the element ytterbium. Acting like 21st-century pendulums or metronomes, the experimental atomic clocks have set a new record for stability, researchers said.
According to an NIST release, the clock's stability is derived from how precisely the duration of each tick matches every other tick. The ytterbium clock ticks are stable to within less than two parts in one quintillian (1 followed by 18 zeros), which is around ten times more precise than the best results for other atomic clock, scientists said.
Researchers built these atomic clocks by trapping thousands of ytterbium atoms at high density. Each ytterbium clock depends on about 10,000 rare-earth atoms cooled to 10 microkelvin, or 10 millionths of a degree above absolute zero. The atoms are trapped in in optical lattice made of laser light. Another laser that "ticks" at a the incredible rate of 518 trillion times per second instigates a transition between two energy levels in the atoms. The massive number of atoms is the key to the clocks stability, researchers explained.
The clock's high level of stability means it can make real-time measurements very quickly, which could have importance for a variety of industrial and environmental applications. NIST writes that the new super-accurate ytterbium chronometer has the potential for making important impacts on a wide range of sensors measuring quantities that have tiny effects on the ticking rate of atomic clocks, such as gravity, magnetic fields, and temperature.
The ticks of any atomic clock must be averaged for a period of time to achieve the best results. A significant benefit of ytterbium clock's stability is that precise results can be achieved very rapidly, the authors said. For comparison, the current U.S. civilian time standard–the NIST-F1 cesium fountain clock–must be averaged for about 400,000 seconds–or five days–for best performance. The new ytterbium clocks can produce the same result in about one second of averaging time.
"The stability of the ytterbium lattice clocks opens the door the to a number of exciting practical applications of high-performance timekeeping," said NIST physicist Andrew Ludlow.
Ytterbium, with the symbol Yb and an atomic number of 70, is a rare earth metal that is soft, malleable, and ductile. It is usually found with other rare earth elements and is most often recovered commercially from monazite sand. It was discovered by Swiss chemist Jean Charles Galissard de Marignac in 1878 and named after the Swedish village Ytterby located near the spot where he found the new mineral. It was not until 1953, however, that scientists precisely determined Ytterbium's chemical properties.
Details of the ytterbium clock experiments have been published in the journal Science Express.
