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Blue laser regulates 'super-accurate' atomic clock

12 Dec 2006

A highly stable blue laser provides the key to controlling the most precise "ticks" ever recorded in a strontium-based atomic clock.

Using an "ultra-stable" blue laser to manipulate strontium atoms trapped in a lattice made of light, scientists at JILA, a joint institution of the US National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder, have produced the most precise "ticks" ever recorded in an optical atomic clock (Science 314 1430).

Besides timekeeping, JILA's strontium lattice may have applications in precision measurements of high frequencies and quantum computing.

The JILA clock design is described as a candidate for next-generation atomic clocks operating at optical frequencies, which divide time into much smaller and more precise units than the microwaves used in today's standard atomic clocks.

The research team, led by NIST Fellow Jun Ye, achieved the highest "resonance quality factor" - which indicates strong, stable signals when a very specific frequency of laser light excites the atoms - ever recorded in coherent spectroscopy, or in studies of interactions between matter and light.

"We can define the center, or peak, of this resonance with a precision comparable to measuring the distance from the Earth to the sun with an uncertainty the size of a human hair," said co-author Martin Boyd.

Although the new strontium clock currently is less accurate overall than NIST's mercury ion clock, it is among the best optical atomic clocks described to date in the published literature. And because it produces much stronger signals, its "resonant" frequency was measured with higher resolution than in the mercury clock.

Improved time and frequency standards have many applications. For instance, ultra-precise clocks can improve synchronization in navigation and positioning systems, telecommunications networks, and wireless and deep-space communications.

Better frequency standards can also be used to improve probes of magnetic and gravitational fields for security and medical applications, and to measure whether "fundamental constants" used in scientific research might be varying over time - a question that has enormous implications for understanding the origins and ultimate fate of the universe.

The JILA research is supported by NIST, the Office of Naval Research and the National Science Foundation.

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