Demonstration of a state-insensitive, compensated nanofiber trap

We report the experimental realization of an optical trap that localizes single Cs atoms 215nm from the surface of a dielectric nanofiber. By operating at magic wavelengths for pairs of counterpropagating red- and blue-detuned trapping beams, differential scalar light shifts are eliminated, and vector shifts are suppressed by 250. We thereby measure an absorption linewidth Γ/2π=5.7±0.1MHz for the Cs 6S _1/2, F=4→6P _3/2, F ^′=5 transition, where Γ ₀/ 2π=5.2MHz in free space. An optical depth d66 is observed, corresponding to an optical depth per atom d ₁0.08. These advances provide an important capability for the implementation of functional quantum optical networks and precision atomic spectroscopy near dielectric surfaces.