Directing a Cloud of Atoms

Capturing atoms. Positioned upside down, the chip is placed in a glass cell where it captures and holds a cloud of atoms in place.

Atoms acting in perfect unison have been corralled and steered on an electronic chip for the very first time. The atom microtrap, described in the 4 October issue of Nature, offers researchers a new and relatively simple tool for manipulating a "cloud" of atoms, and could prove useful in building a quantum computer.

When chilled to almost absolute zero, atoms condense into a single quantum state: like majorettes marching, their motions become synchronized and the entire band of atoms shares the same quantum qualities. Researchers first produced atom clouds, an example of a Bose-Einstein condensate, 6 years ago. Now, physicists at the Max Planck Institute for Quantum Optics in Munich, Germany, have manipulated a Bose-Einstein condensate as it floated above the surface of a chip.

Physicist Jakob Reichel and his colleagues began with a circuit board with tiny current-carrying gold wires on its surface. The magnetic fields from these wires, combined with an external magnetic field bathing the device, produced a magnetic cage about a millimeter in diameter. Then, the scientists used a laser beam and a special trapping current on the chip to guide a vapor of free-floating rubidium atoms into the trap. Finally, they tweaked the magnetic fields to deflate and cool the atom ball, creating the condensate. To demonstrate the chip's potential, the researchers used a special pair of wires to nudge the hovering atom ball 1.6 millimeters across the chip. Chip-trapped atoms have been around for a couple of years, explains Reichel, but on the new device, he says, "all the atoms are in the same quantum state, which makes it easier to observe the wave nature of the particles."

Creating this kind of atom condensate may open the door to chip-based atom lasers, precisely controlled beams of atoms. Trapping a cloud of cold atoms on a chip is also a necessary prerequisite to building so-called quantum computers, elusive machines that exploit the laws of quantum mechanics. "The present work is a milestone in this direction," says Peter Zoller, a physicist at the University of Innsbruck in Austria.

Related sites

Integrated magnetic traps for neutral atoms
Centre for Quantum Optics and Quantum Information

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