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Optical One-Way Barrier for Atoms

Daniel Steck, University of Oregon

(Session 5 : Friday from 5:00-7:00)

Abstract. We demonstrate an asymmetric optical potential barrier for ultracold ⁸⁷Rb atoms using laser light tuned near the D₂ transition. Such a one-way barrier, where atoms impinging on one side are transmitted but reflected from the other, is a literal realization of Maxwell's demon and has important implications for cooling atomic species not amenable to standard laser-cooling techniques. In our experiment, atoms are confined to a far-detuned dipole trap consisting of a single focused Gaussian beam, which is divided near the focus by the barrier. The one-way barrier consists of two focused laser beams oriented normal to the dipole trap. The first barrier beam is tuned between the F = 1 → F' and the F = 2 → F' families of hyperfine transitions, and presents a barrier only for atoms in the F = 2 ground state, while letting F = 1 atoms pass. The second beam pumps the atoms to F = 2 on the reflecting side of the barrier, thus producing the asymmetry. We study experimentally the reflection and transmission dynamics of atoms in the presence of the one-way barrier.