Sub-second Coherence Against Infrared Radiation of an Atomic Cloud Trapped in a 1D Optical Lattice Superimposed on a Magic Magnetic Trap below a Persistent Supercurrent Atom Chip*

We tried to extend the coherence time of a trapped atomic cloud against D₁-line stimulated Raman transition. As far as internal state operations of atoms are carried out for millisecond or longer, the atomic cloud must be confined in a trapping potential. The trapping potential for neutral atoms is usually constituted with an inhomogeneous magnetic or optical field, and induces energy shift, which generally causes the difference of time evolution of atomic wave function and reduces the coherence time of the trapped atomic ensemble. The coherence time of trapped atomic cloud is also limited by the other factors, e.g., atom-atom collisions, environmental noise, spontaneous emission from the intermediate states, Gaussian beam profile of interacting field, and photon recoil of Raman transitions. To ameliorate these influences, we employed a 1-dimensional optical lattice potential superimposed on a field insensitive (magic field) magnetic trap below a persistent supercurrent atom chip. With this setup we obtained sub-second T₂ coherence time measured with the Ramsey interferometric technique.