One‐atom laser: Trapped atom shoots steady light beam

Gary Taubes

The word laser has taken on a new meaning: a beam of atoms marching in quantum lockstep, like the photons of a light laser. Two years ago, physicists achieved the crucial starting point for an atom laser, which could aid everything from atomic clocks to chipmaking, when they created an exotic brew of atoms all merged in a single quantum state. Now, a group at the Massachusetts Institute of Technology reports in this issue ( p. 637 ) that they have shaped this “Bose-Einstein condensate” into pulses, each one a single, coherent “matter wave.”

Chun-Chia Chen, Shayne Bennetts, Rodrigo González Escudero +2 more

David Guéry-Odelin

Charles Seife

For years, physicists have been slowing light down to a crawl, and even stopping it in its tracks, by shooting laser beams into cold gases known as Bose-Einstein condensates. Now, researchers have done the same thing in a much less exotic solid. The advance may one day lead to memory devices for computers that store information on beams of light.

Charles Samuels

Lev Khaykovich, Nir Davidson

We analyze the light-induced atom–atom interactions in optically thick atomic clouds and show that, when the laser frequency is on-resonance with the atomic transition, they become attractive. On the basis of this analysis we propose and demonstrate a novel scheme to compress a cold and dense atomic cloud with a short on-resonance laser pulse. The compression force arises from attenuation of the laser light by the atomic cloud. The following free propagation of the atoms shows a lenslike behavior that yields a transient density increase at the focal time, where neither laser nor magnetic field perturbations exist. A cooling pulse, which is applied at the focal time of this lens, restores the initial temperature of atoms, and hence the phase space density is increased. Finally, we adopt our compression scheme to a quasi-steady-state mode by temporally chopping it with the cooling and trapping beams of a magnet-optical trap.