Ultracold Atoms Form Long-Lasting Waves

Scientific American ^ | FR Post 5-29-02 | Editorial Staff--Kate Wong

[vannrox]

Ultracold Atoms Form Long-Lasting Waves

At sufficiently cold temperatures, the atoms in a gas can form what is known as a Bose-Einstein condensate (BEC), losing their individual identities and merging into a single quantum state. The phenomenon has fascinated physicists ever since gaseous BECs were created in the laboratory in 1995 (although the possiblity was first postulated some 70 years earlier), and a flurry of recent research has uncovered all kinds of remarkable condensate properties. Now researchers writing in the journal Nature have yet another discovery to add to that list. According to the report, BEC atoms trapped in a thin beam of light and forced to march single file can form atom waves that maintain a constant shape while propagating.


In their experiments, Randall G. Hulet of Rice University and his colleagues observed localized wave packets, or solitons, of lithium atoms traveling great distances--over a period of up to several seconds--without spreading. Caravans of up to 15 solitons were detected. The key appears to have been causing the atoms to attract one another, thus offsetting their natural tendency to disperse. Although this represents the first observed instance of so-called bright matter-wave soliton trains, localized wave bundles themselves are well known in high-speed optical communications networks, in which solitons of light enable the transfer of data across great distances without the help of signal boosters.


If you're wondering what, exactly, such atomic soliton trains might be useful for down the road, the short answer is that it's difficult to say. The authors speculate, however, that precision measurement applications such as atom interferometry might benefit from an atomic soliton laser, based on solitons like the ones they observed. "Forty years ago no one imagined that lasers would be used to play music in our cars or scan our food at the grocery store checkout," Hulet muses. "We're getting our first glimpse of a wondrous and sometimes surprising set of dynamic quantum phenomena, and there's no way to know exactly what may come of it." --Kate Wong

[callisto]

This is a 3D rendering of a matter-wave soliton train, a succession of special waves made of self-attracting ultracold atoms. Each peak in the train is a Bose-Einstein condensate, a localized collection of atoms cooled to nearly absolute zero temperature. Solitons are unusual bundles of waves, constrained to move in only one dimension. Perhaps the most striking feature of solitons is that they propagate without spreading; ordinary waves spread out and lose their original shape as they propagate. Solitons have been observed in many wave phenomena, such as the motion of water waves in narrow canals, and light pulses in optical fibers. Advanced optical communications systems employ solitons because ordinary light pulses spread and require frequent signal boosters. The atom-wave solitons shown in the figure may someday be useful for an atom laser.

Reported by: K.E. Strecker, G. Partridge, A.G. Truscott , and R.G. Hulet, Nature, 9 May 2002; advance online publication, 1 May 2002 (DOI 10.1038/nature747).
Physics News Update item on this research
Rice University News Release on this Paper
Rice Atomcool! Website

[Brett66]

If you're wondering what, exactly, such atomic soliton trains might be useful for down the road, the short answer is that it's difficult to say.

Maybe a particle beam weapon?

[gcruse]

As a light-pointer for a slide presentation? ;)

[petuniasevan]

Quantum soliton PING!