József Fortágh
Ultracold atoms near Superconductors
B. Kasch, H. Hattermann, D. Cano, F. Jessen, T. Judd, R. Kleiner, C.
Zimmermann, D. Koelle, and J. Fortágh
Universität Tübingen
Physikalisches Institut and Center for Collective Quantum Phenomena and
their Applications
Auf der Morgenstelle 14, D-72076 Tübingen, Germany
http://www.pit.physik.uni-tuebingen.de/fortagh/
The coupling of ultracold atoms with solid state devices has generated considerable interest as a versatile approach towards creating hybrid quantum systems with exciting applications for precision measurements and quantum information processing. We report here on our approach towards the realization of such systems and present measurements on
ultracold atoms in the vicinity of superconducting surfaces serving as microtraps for the cold atoms. Our experimental setup consists of a rubidium Bose-Einstein condensate apparatus and optical tweezers for transporting ultracold atom clouds to the surface of a thermally shielded helium flow cryostat at 4.2 K. Atom clouds are subsequently loaded into a magnetic microtrap formed by a 125 micron diameter superconducting niobium wire. By monitoring the atom cloud, we observe
that the Meissner effect shortens the distance between the trap and the superconductor, reduces the magnetic field gradients, lowers the trap depth, and alters the trapping frequencies [1]. The experimental data are explained by the London theory [2]. We also present data on the spin coherence of atoms near cryogenically cooled surfaces. We observe a
significant increase of the magnetic trap lifetime near superconducting niobium as compared to normal conducting copper at the same temperature. The data indicates the absence of Johnson-noise induced spin-flips near superconductors [3].
[1] D. Cano, B. Kasch, H. Hattermann, R. Kleiner, C. Zimmermann, D.
Koelle, J. Fortágh, Phys. Rev. Lett. 101, 183006 (2008).
[2] H. D. Cano, B. Kasch, H. Hattermann, D. Koelle, R. Kleiner, C.
Zimmermann, J. Fortágh, Phys. Rev. A 77, 063408 (2008).
[3] B. Kasch, H. Hattermann, D. Cano, T. E. Judd, S. Scheel, C.
Zimmermann, R. Kleiner, D. Koelle, and J. Fortágh, Lifetime Measurements
of Ultracold Atom Clouds Near Cryogenic Surfaces; arXiv:0906.1369v1.
