Coherence Properties of Nanofiber-Trapped Cesium Atoms

We experimentally study the ground state coherence properties of cesium atoms in a nanofiber-based two-color dipole trap, localized similar to 200 nm away from the fiber surface. Using microwave radiation to coherently drive the clock transition, we record Ramsey fringes as well as spin echo signals and infer a reversible dephasing time of T-2* = 0.6 ms and an irreversible dephasing time of T-2' 3.7 ms. By modeling the signals, we find that, for our experimental parameters, T-2* and T-2' are limited by the finite initial temperature of the atomic ensemble and the heating rate, respectively. Our results represent a fundamental step towards establishing nanofiber-based traps for cold atoms as a building block in an optical fiber quantum network.