Quantum queerness gets quick, compact

The bizarre form of matter called the Bose-Einstein condensate affords physicists an extraordinary way to study the quantum world. Scientists hope also to make practical use of these clouds of frigid atoms that share the same quantum state. Among the technologies they have in mind are quantum computers and accelerometers for measuring gravity with unmatched precision.

In a laser trap, several Bose-Einstein condensates (distinct blobs) in different magnetic states can coexist. Barrett et al./PRL

So far, however, the cumbersome equipment needed to make these condensates has hindered the development of such gadgetry. Researchers typically use magnetic traps that cover whole tables. These devices take as long as a minute to produce a condensate, too long for such uses as quantum computing.

Separate teams in the United States and Germany now report progress toward faster, more compact machines for making condensates.

Michael S. Chapman and his colleagues at the Georgia Institute of Technology in Atlanta have slashed the time to condense a gas of already chilled atoms to about 2 seconds. They achieved this by eliminating the magnetic trap commonly used at the end of the multistep process of condensing rubidium-87 atoms. Instead, the researchers caught atoms in the crossfire of two carbon-dioxide laser beams.

The crossed beams cool the rubidium cloud to nearly absolute zero by allowing the higher-energy–in essence, warmer–atoms to escape as the researchers lower the beams’ power. This dramatic cooling triggers the remaining atoms to coalesce into a condensate. Presumably, condensation happens quickly because this laser step yields tighter-packed atoms, Chapman says. The team describes its method in the July 2 Physical Review Letters.

This so-called all-optical approach should expand the range of atoms and molecules that scientists can condense, Chapman adds. That’s because it should work on particles regardless of the orientation of their intrinsic magnetism, or spin. Magnetic traps retain and cool only those particles of a particular spin direction.

In another approach toward technology based on Bose-Einstein condensates, two separate German teams–one at the University of Tübingen and one at the Max Planck Institute for Quantum Optics in Garching–announced in June that they had condensed rubidium atoms in magnetic traps spanning only tens of micrometers. In those snug traps, the final condensation of the atoms, which the researchers had prechilled by other means, also took place in just seconds.

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