Quantum optics with ultra cold atoms

In this project, experiments will be carried out that are concerned with the laser-optical preparation, manipultion, and investigation of atoms. The atoms will be trapped and cooled by laser light, and then studied spectroscopically. The investigation is directed particularly at the quantum mechanical properties of a small number of trapped ultra cold atoms. Systems of small numbers of particles are particularly interesting because they exhibit the nature of quantum mechanical processes in a particularly conspicuous way. This project deals with two regimes of small numbers of quanta of motional energy, corresponding to the low temperature of the atoms. This combination creates new quantum mechanical phenomena which in this project will be investigated for the first time. Starting with a large number of Rubidium atoms that are trapped and precooled in a magneto-optical trap, a fraction of these atoms is loaded into a novel optical dipole trap. This trap consists of six laser beams which overlap in one spot and interfere in pairs. The light frequency is tuned to the high energy side of an atomic resonance. This arrangement creates a 3-dimensional, approximately harmonic, conservative potential with a diameter of about 10 mu-m. The atoms are cooled further with optical cooling techniques which have so far been applied to single trapped ions in Paul traps. The aim of the cooling is to bring several atoms into the ground state of the trap potential such that a quantum degenerate ensemble is created. This degenerate ensemble will eventually be studied quantum optically, in particular with respect to its quantum mechanical state of motion, its internal interactions and its interaction with light. The effect of the number of particles in the ensemble on these quantum mechanical properties will also be investigated.