A True One-Dimensional Atomic System

A true one-dimensional atomic system, consisting of a Bose Einstein condensate (BEC) of rubidium atoms pulled out into a thin tubelike shape, has been experimentally demonstrated for the first time, in the ETH lab in Zurich.

The ETH researchers begin by loading their condensate into an optical lattice, an artificial configuration in which atoms are held and moved about in 3D space by criss-crossing beams of laser light. In contrast to previous efforts to make one-dimensional BECs, this experiment succeeded in extruding a condensate into 1000 small needle-like condensates---one dimensional strings of 100 atoms or so and not merely cigar shaped lozenges---because they used a far more intense laser trapping field and higher quality laser beams (more truly Gaussian in their profile), the better to keep atoms from tunneling from one needle into a neighboring needle (see figure).

Once the ETH physicists had established their one-dimensional atomic gas what did they do with it? They set their lean stack of atoms into motion by slightly moving the magnetic center of their apparatus. This caused the atoms to move up and down in a "breathing mode"at a characteristic frequency. Studying this oscillation was analogous to listening a one dimensional bell ringing.

How unusual is the ETH 1D condensate? Well, even two dimensional atomic systems are rare in physics: helium films and hydrogen atoms sitting atop helium are the prominent examples. The only other 1D gas studied in physics consists of electrons moving in "quantum wires."

One-dimensional systems are interesting because they are more intrinsically dominated by quantum effects than 2- or
3-dimensional systems. According to Tilman Esslinger (tilman.esslinger@iqe.phys.ethz.ch, http://www.quantumoptics.ethz.ch/) 1D ensembles of atoms should play an important role wherever precision handling of atoms is needed: in atom optics, atom interferometry, or sending signals from atom lasers down an atom waveguide. (Moritz et al., Physical Review Letters, 19 December 2003.)