Magazine article Science News

Ultracold Atoms: New Gravity Yardstick?

Magazine article Science News

Ultracold Atoms: New Gravity Yardstick?

Article excerpt

The laboratory feat of laser-cooling atoms to near absolute zero is verging on its first commercial application.

A prototype of a novel, laser-cooled device for measuring gravity, described in the Aug. 3 Physical Review Letters, promises to be a boon for oil exploration, geophysical measurements, and military uses, says Mark A. Kasevich, the Yale University physicist leading the U.S. Navy-funded development team. "I think there's a possibility for a basic science idea to have an impact technologically," he says.

Nobel prize-winning techniques developed in the 1980s to slow, and thus cool, atoms by zapping them with laser-generated photons have led to stunning advances in physics, including the creation of Bose-Einstein condensates, which are ultracold clusters of atoms sharing one quantum state (SN: 7/25/98, p. 54). The only practical gadget to emerge from the field, however, has been a better atomic clock, attractive only to a few time-standard labs, says Steven L. Rolston at the National Institute of Standards and Technology in Gaithersburg, Md.

The newer instrument determines gravity's gradient, or change in strength with position, by comparing the gravitational acceleration of two clouds, each made up of millions of cesium atoms. The clouds are cooled to 3 microkelvins and spaced a meter apart. Observing interference within each cloud's quantum-mechanical wave behavior yields a precise measurement of gravity at that position.

"It's beautiful work," Rolston says. "It's nice to see something showing some true practicality. …

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