Atomic
clocks based on the oscillations of a cesium atom keep amazingly steady
time and also define the precise length of a second. But cesium clocks
are no longer the most accurate. That title has been transferred to an
optical clock housed at the U.S. National Institute of Standards and
Technology (NIST) in Boulder, Colo. that can keep time to within 1
second in 3.7 billion years. Before this newfound precision can redefine
the second, or lead to new applications like ultra-precise navigation,
the system used to communicate time around the globe will need an
upgrade. Recently scientists from the Max Planck Institute of Quantum
Optics, in the south of Germany, and the Federal Institute of Physical
and Technical Affairs in the north have taken a first step along that
path, successfully sending a highly accurate clock signal across the
many hundreds of kilometers of countryside that separate their two
institutions.
The
researchers will present their finding at Conference on Lasers and
Electro Optics (CLEO: 2012), taking place May 6-11 in San Jose, Calif.
"Over
the last decade a new kind of frequency standard has been developed
that is based on optical transitions, the so-called optical clock," says
Stefan Droste, a researcher at the Max Planck Institute of Quantum
Optics. The NIST optical clock, for example, is more than one hundred
times more accurate than the cesium clock that serves as the United
States' primary time standard.
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