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17 Jun 2002
US scientists have pioneered the first all-optical technique for producing Bose Einstein condensates.
Researchers at the Georgia Institute of Technology, US, have developed a method to super cool atoms to form a single quantum state, the so-called Bose Einstein condensate, in just two seconds.
In the past, scientists have relied on unwieldy magnetic coils to cool atoms and produce a condensation in which millions of atoms fall into a single quantum state. However, by focusing two crossed carbon dioxide laser beams on a cloud of rubidium atoms, Michael Chapman and colleagues were able to trap and then cool the atoms into a Bose Einstein condensate (BEC).
"In optical traps, the simplest way to force evaporation is to lower the trap depth by decreasing the power in the beams," said the researchers in Phys. Rev. Letts 871. Careful control of the evaporative cooling rate allowed Chapman and his colleagues to cool 35 000 atoms tantalizingly close to absolute zero so they collapsed into a single quantum state.
"This is quite exciting from a physics standpoint, because it is a whole new aspect of Bose Einstein condensation that wasn't considered by Bose or Einstein," said Chapman. "The simplicity and the speed of the technique are quite remarkable."
Although magnetic methods have produced condensates that contain millions of atoms, Chapman is convinced that the optical technique will scale up in time. The technique also allows atoms with magnetic moments, such as magnesium and strontium that are not suitable for magnetic traps, to be studied.
"Where this will lead is hard to predict," added Chapman. "But historically, whenever we've been able to get control over physical systems, it has led to dramatic new directions in science and technology."
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