Quantum theory of an atom laser originating from a Bose-Einstein condensate or a Fermi gas in the presence of gravity

TL;DR

This paper develops a comprehensive 3D quantum mechanical model for atom lasers from Bose-Einstein condensates and Fermi gases under gravity, predicting outcoupling rates, beam profiles, and effects of interactions and superfluidity.

Contribution

It introduces a detailed quantum theory for atom lasers including interactions and fermionic effects, extending previous models and aligning with experimental data.

Findings

Interactions enhance interference in the beam profile.

Atomic interactions modify the outcoupling rate.

The formalism applies to both bosonic and fermionic gases.

Abstract

We present a 3D quantum mechanical theory of radio-frequency outcoupled atom lasers from trapped atomic gases in the presence of the gravitational force. Predictions for the total outcoupling rate as a function of the radio-frequency and for the beam wave function are given. We establish a sum rule for the energy integrated outcoupling, which leads to a separate determination of the coupling strength between the atoms and the radiation field. For a non-interacting Bose-Einstein condensate analytic solutions are derived which are subsequently extended to include the effects of atomic interactions. The interactions enhance interference effects in the beam profile and modify the outcoupling rate of the atom laser. We provide a complete quantum mechanical solution which is in line with experimental findings and allows to determine the validity of commonly used approximative methods. We also extend the formalism to a fermionic atom laser and analyze the effect of superfluidity on the outcoupling of atoms.