Ultracold atoms near superconductors and carbon nanotubes

Abstract:Hybrid quantum systems, which combine ultra-cold atoms with solid state devices, have attracted considerable attention in the last few years. Promising applications are in the areas of precision sensing and quantum information processing. I report on our experimental efforts towards the realization of such systems based on ultracold atoms, superconductors and carbon nanotubes. The cold atom/superconductor experiment consists of a rubidium BEC apparatus and a thermally shielded helium flow cryostat at 4.2 K in the same ultrahigh vacuum system. Atom clouds are loaded into a magnetic microtrap formed near a superconducting niobium wire. We observe the impact of the Meissner effect on the trap parameters and measure the spin coherence of atoms near the superconductor. The measured coherence times are the longest yet observed in the vicinity of a highly conducting material and confirm the suppression of Johnson noise in superconductors. The results have implications for the development of coherently coupled cold atom/solid state quantum devices, in which cold atoms serve as long term quantum memory. In a second experiment, we investigate the interaction between ultracold atoms and carbon nanotubes. Free standing single nanotubes, periodic structures, and “carpets” of nanotubes are grown on the surface of an atom chip. We observe the scattering of ultracold atoms on the nanotubes. In addition, we describe a novel atom detector based on field ionization of ground state atoms near carbon nanotubes and subsequent ion counting.