A Magnetic Waveguide for Bose-Einstein Condensates

When Bose-Einstein condensation (BEC) was first observed in an ultracold atomic vapor, it was widely applauded as a remarkable achievement of modern physics. The BEC transition is marked by the occupation of a single quantum wave function by a large number (10⁶)of atoms, and the condensate therefore illustrates the wave/particle duality principle of quantum mechanics with unprecedented force. One of the reasons for the widespread interest in BEC is that it provides a simple and powerful example of this basic principle of quantum theory. Another reason, however, is that condensates may prove to be a useful tool. Their wave nature suggests applications similar to those of optical lasers, which have proven to be immensely valuable. To give two examples, condensates should be ideal sources for atom interferometers, and the highly coherent atoms they contain might also serve as information carriers for quantum computing.

These and other applications will be discussed below, but one common difficulty they face is the need for a way to transport the condensate to a desired location. For laser light, this is accomplished with mirrors and lenses, and by analogy similar mechanisms for atoms are referred to as atom optics. Unfortunately, satisfactory atom optics elements are not available. To illustrate the problem, consider an atom interferometer, a condensate must be coherently separated into two pieces, which then proceed along different paths until being recombined at a later point. The ability to coherently split a condensate has been demonstrated, but good techniques to controllably direct and recombine the two components are lacking.