Synopsis: Cold atoms on a one-way ticket

Lasers can confine atoms in one-dimensional traps. Now, the right superposition of lasers can act as one-way barriers that let atoms move in one direction, but not the other.
Synopsis figure

In 1871, James Clerk Maxwell imagined a demon perched on a wall separating two rooms, opening a small trapdoor to let fast atoms pass from left to right and slow atoms right to left. Soon, all the hot gas would be on one side, and the cold gas on the other, causing entropy to decrease rather than increase. We now know that the demon itself must increase in entropy, so the second law of thermodynamics is safe. But as Jeremy Thorn, Elizabeth Schoene, Tao Li, and Daniel Steck of the University of Oregon report in the 20 June 2008 issue of Physical Review Letters, it is possible to build the demon’s trapdoor.

Several groups have proposed variants on a one-way gate or “atom diode”. In their version, the Oregon researchers use a laser to confine cooled 87Rb atoms to a one-dimensional optical trap. A one-way barrier is formed by directing two other laser beams nearly normal to the trap: one beam is tuned so that an atom passing through it is placed in an excited state, while a second adjacent laser provides either a potential barrier or an open path, depending on whether the atom is excited or not. Ground state atoms hitting the barrier beam directly will pass through, but atoms excited by the laser on the other side will be reflected.

These kinds of control techniques may be useful for studying atom trapping, as well as for “atom on a chip” technologies such as miniature atomic clocks. - David Voss


Announcements

More Announcements »

Subject Areas

Atomic and Molecular Physics

Previous Synopsis

Superconductivity

Back to basics

Read More »

Next Synopsis

Superconductivity

At last, single crystals

Read More »

Related Articles

Synopsis: A Crystal of Light and Atoms
Atomic and Molecular Physics

Synopsis: A Crystal of Light and Atoms

A predicted type of atom-light crystal could host phonon-like excitations, allowing for new ways to simulate the physics of solids.   Read More »

Viewpoint: An Arrested Implosion
Condensed Matter Physics

Viewpoint: An Arrested Implosion

The collapse of a trapped ultracold magnetic gas is arrested by quantum fluctuations, creating quantum droplets of superfluid atoms. Read More »

Synopsis: No Vacancy for Tunneling
Atomic and Molecular Physics

Synopsis: No Vacancy for Tunneling

The tunneling rate for cold atoms in an optical lattice can be made to depend on whether a neighboring site is occupied—a behavior that may reflect the tunneling in complex materials. Read More »

More Articles