Guiding of matter waves in a manner similar to the guiding of light in optical fibers has been the subject of several theoretical and experimental studies. Such matter waveguides could significantly boost the development of atom optical devices like interferometers and pave the way to their future application as highly sensitive sensors for rotation and acceleration. Hollow core photonic bandgap (HCPBG) fibers are a promising candidate for matter waveguides. To the best of our knowledge, our experiment is the first to achieve guiding of slow, cold atoms through a HCPBG fiber.

Our setup is shown conceptually in the figure. A high power guiding light field is coupled into the HCPBG fiber and impinges on a cloud of cold Rubidium atoms at the fiber's exit. The field induces an ac-Stark shift of the atoms' ground state allowing them to minimize their energy by moving to regions of highest intensity. Consequently, atoms are accelerated towards the fiber tip, propagate through the fiber and leave the fiber after a transit time determined by the kinetic energy gained during the acceleration. The atoms are then illuminated by a resonant, retroreflected detection beam in order to balance the radiation pressure. By imaging the guided atoms' fluorescence signal, we observe an atomic flux for 50 ms which peaks at 1.2 x 10⁵ atoms/s (see graph to the right) corresponding to a total number of 7400 atoms. The results are in good agreement with the theoretical predictions based on the properties of the guiding potential.

The study demonstrates the feasibility of long distance guiding of cold atoms. Singlemode operation of the waveguide appears to be within reach by cooling the atoms into their transversal ground state. Our system has potential applications as a continuous atom laser, a guided matter wave interferometer and as a model system for studying one dimensional quantum gases.

Preprint arxiv:1010.0101