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Laser cages control unruly atoms

作者:溥蹑    发布时间:2019-03-02 06:19:02    

By Tom Simonite (Image: Peder Sjölund) Trapping unruly atoms within laser lattices brings order to their motion, researchers say. A team of Swedish scientists used an array of 20 lasers to trap a cloud of randomly moving super-cooled atoms. Once caught, the lasers gave the atoms an energy kick that caused them to move in one direction. Controlling the energy transfer from lasers to atoms in this way could eventually be useful in nano-engineering. Peder Sjölund and Anders Kastberg from Umeå University in Sweden used a technique called laser cooling to trap and control a cloud of Caesium atoms. This involves cooling the atoms to just above absolute zero, which slows their microscopic random Brownian motion from hundreds of kilometres per hour to just a few metres per second. The atoms can then be “locked” in place using a lattice of laser beams. “The lasers create a regular system of atoms, somewhat like a crystal,” says Kastberg. “They work as a kind of egg crate for atoms.” To control the atoms’ movement the researchers exploited the fact that they absorb energy from photons in the beams, which kicks them into motion. Normally this would cause the cloud to drift back into disorder but the researchers used a second, overlapping, laser lattice to encourage the newly energised atoms to move to another position in space. “By setting the position of the two lattices we can make the atoms move in one direction rather than the other,” Kastberg explains. The team were able to control the movement of the cloud in three dimensions, and make it move at a controlled speed of 3 millimetres per second. The researchers believe that the ability to control random motion could prove useful in nano-engineering. Kastberg notes that proteins within living cells also control Brownian motion to carry out routine tasks. “They work on more complicated principles than our system, but our work may provide a way to move nano devices on very small scales,

 

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