Experimental Realization of an Optical One-Way Barrier for Neutral Atoms

TL;DR

This paper demonstrates an optical one-way barrier for ultracold rubidium atoms, enabling asymmetric transmission and reflection, which could advance cooling techniques for atoms and molecules not suitable for standard laser cooling.

Contribution

It presents the first experimental realization of an optical one-way barrier for neutral atoms using laser light tuned near atomic transitions.

Findings

Achieved asymmetric transmission and reflection of ultracold atoms.

Implemented a barrier that depends on atomic hyperfine states.

Potential applications in cooling non-laser-coolable atoms and molecules.

Abstract

We demonstrate an asymmetric optical potential barrier for ultracold 87 Rb atoms using laser light tuned near the D_2 optical transition. Such a one-way barrier, where atoms impinging on one side are transmitted but reflected from the other, is a realization of Maxwell's demon and has important implications for cooling atoms and molecules 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 almost normal to the dipole-trap axis. The first beam is tuned to have a red (blue) detuning from the F=1 -> F' (F=2 -> F') hyperfine transitions, and thus 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.