Observation of coherent internal-state superpositions near a chip surface

Summary form only given. We have created coherent superpositions of the |F = 1, m = -1> and |F = 2, m = 1> states of ⁸⁷Rb in a magnetic chip trap by exciting two-photon (microwave-radiofrequency) transitions. The trap contains ∼10⁴ atoms at a temperature of ∼800 nK. In Ramsey-type measurements, we observe coherence lifetimes in excess of 1 s even for trap-surface distances below 40 μm. This is a very encouraging result for "atom-chip" applications in quantum information and atom interferometry.