Experiments with Ultracold Helium Atoms

Claude COHEN-TANNOUDJI

College de France and Laboratoire Kastler Brossel
Ecole Normale Superieure, Paris, France

Helium atom is a simple atom with two isotopes, a bosonic one (He4) and a fermionic one (He3). Optical pumping of He3 has allowed one to get one of the first evidences of quantum transport phenomena in polarized quantum fluids. More recently, laser cooling of He4 in the metastable state 23S1 has opened the way to several new investigations: laser cooling below the single photon recoil limit and connections with L?vy flights; Bose Einstein condensation of atoms in a metastable state; production of ultracold molecules formed by two metastable atoms by photo-association; dark states involving coherent superpositions of molecular states and states of a pair of colliding atoms; bunching and antibunching behaviour of bosonic and fermionic atoms. A brief review of these experiments will be presented, showing the evolution of ideas in this field.