Theory of atom lasers
The extraction of a coherent beam of atoms from a Bose Einstein Condensate (BEC) of cold atoms gives rise to an atom laser.
We are interested in the theoretical description of the outcoupling rate of an atom laser (the total current) and the profile of the beam. The description in terms of a source (the BEC) and the Green function of the propagating state (the atom laser) provides a consistent framework for predicting and analyzing an atom laser [4,16].
Starting from a non-interacting system [3], we can include interactions via a mean-field approach, and also include higher occupied trapping modes [16]. Interactions can lead to a splitting of the beam, which has been observed experimentally.
Our analytical-solvable model is three-dimensional and quantum mechanical. It compares very well with available experimental data and predicts some interesting features of matter waves from microtraps:
- The gravitational field provides a virtual double slit, which leads to an interference pattern [4,7,16].
- It shows that the outcoupling of atoms is not spatially limited to a classical resonance slice through the condensate.
Another line of research concerns time-dependent trapping potentials for cold atoms. Here, we derive an analytic solution for the propagation out of an (with time less) attractive potential, which is embedded in a long-range repulsive potential [10].
 |
 |
| (a) Vortices [4] | (b) Beam splitting [3,16] |
References
| [16] | Quantum theory of an atom laser originating from a Bose-Einstein condensate or a Fermi gas in the presence of gravity | ||
| T. Kramer and M. Rodríguez | |||
| Phys. Rev. A, 74, 013611-1-13, (2006) | article | arxiv | |
| [10] | Tunnelling out of a time-dependent well | ||
| T. Kramer and M. Moshinsky | |||
| J. Phys. A, 38, 5993-6003, (2005), AMS Review MR2167958 | article | arxiv | |
| [7] | Matter waves from localized quantum sources | ||
| T. Kramer | |||
| Squeezed States and Uncertainty Relations, Edited by H. Moya-Cessa et al., pp. 210-217, Rinton Press, Princeton, NJ (2003) | book | arxiv | |
| [4] | Ballistic matter waves with angular momentum: Exact solutions and applications | ||
| C. Bracher, T. Kramer, and M. Kleber | |||
| Phys. Rev. A, 67, 043601, (2003) | article | arxiv | |
| [3] | Matter waves from quantum sources in a force field | ||
| T. Kramer, C. Bracher, and M. Kleber | |||
| J. Phys. A: Math. Gen., 35, 8361, (2002) | article | arxiv | |