The most accurate atomic clock in the world constructed

Two ytterbium clouds make the atomic clock more reliable and faster than any other

Look at one of the new Ytterbium atomic clocks. Inn her are ultracold atoms trapped in an optical grating and are excited by a measuring laser. © N. Phillips / NIST
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Double time measurement: US researchers have constructed the world's most accurate atomic clock so far. Each "tick" of this clock deviates by less than a trillionth of a second from the duration of the previous one. The highlight: This optical atomic clock consists of two clouds of ytterbium atoms. This design allows faster and more reliable measurements, as the researchers report in the journal Nature Photonics.

Atomic clocks are clocking the world. The clocks based on the vibrations of ultracold cesium atoms are the reference for the world time and ensure, for example, that the GPS satellites provide accurate location data. But there are even more precise and precise timers: In 2015, US researchers constructed a strontium atomic clock that would not go by for a second in 15 billion years. It is even precise enough to measure Einstein's time-stretching by gravity on Earth.

Double ytterbium cloud

Andrew Ludlow of the National Institute of Standards and Technology (NIST) in Boulder and his colleagues have gone one step further. In their new atomic clock ytterbium atoms serve as a clock. As typical for optical watches, they are irradiated with a laser. The light frequency at which the atoms change their energy state serves as a reference for the second.

In contrast to the common cesium clocks or the high-precision strontium clock, the new atomic clock combines two ultra-cold atom clouds - one with 5, 000 and one with 10, 000 ytterbium atoms. Both clouds are irradiated by a measuring laser. As a result, tiny deviations in the laser frequency and thus in the "ticking" of this clock can be detected and corrected directly during the measurement.

One thousandth of a second measuring time is enough

The big advantage is that the time measurement can be performed ten times faster and more accurately than with other watch models. Because so far, each measurement must have a certain duration to compensate for tiny variations in the tick length. Thanks to the double atom cloud, the Ytterbium atomic clock runs so evenly that a thousandth of a second of measuring time is enough to obtain a reliable time. display

"That means that the deviations in tick duration are less than 1.5 trillionths of a second, " says Ludlow. "Although this clock only slightly outperforms the accuracy of our strontium watch, it achieves that accuracy ten times faster." The clock's performance is thus barely any longer from the laser, but almost exclusively from the atoms themselves,

Can also be used on future satellites

The new Ytterbium atomic clock could be used anywhere in the future, where minute time deviations must be measured quickly and accurately, as the researchers explain. Such an atomic clock would, for example, be useful in the test of Einstein's time-stretching, but also in the study of dark matter and other basic physical questions.

The double atomic clock is still slightly larger than the conventional single clocks. But as the researchers explain, they can be reduced relatively well especially because the built-in tick correction allows a simplification of the laser system. The Ytterbium atomic clock could therefore be used on satellites in the future. (Nature Photonics, 2016; doi: 10.1038 / nphoton.2016.231)

(National Institute of Standards and Technology (NIST), 30.11.2016 - NPO)