Regensburg 2004 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 29: Quantenkoh
ärenz und Quanteninformationssysteme II
TT 29.2: Vortrag
Donnerstag, 11. März 2004, 14:45–15:00, H19
Quantum dissociation of a vortex-antivortex pair in a long Josephson junction — •M.V. Fistul1, A. Wallraff2, Y. Koval1, A. Lukashenko1, B.A. Malomed3, and A.V. Ustinov1 — 1Physikalisches Institut III, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany — 2Dept. Applied Physics, Yale University, New Haven, CT 06520 USA — 3Tel Aviv University, Tel-Aviv, 69978 Israel
Thermal and quantum dissociation of a single vortex-antivortex (VAV) pair in an annular Josephson junction is experimentally observed and theoretically analyzed [1]. VAV pair is confined in a pinning potential controlled by external magnetic field and bias current. The dissociation of the pinned VAV pair manifests itself by a switching of the Josephson junction from the superconducting to the resistive state. The observed temperature and field dependence of the switching current distribution is in agreement with our analysis. In an extremely narrow long JJs (a small width of a JJ allows to decrease the No-dqelectromagneticNo-dq effective mass of a VAV pair) the crossover from the thermal to the macroscopic quantum tunneling mechanism of dissociation occurs at a temperature of about 100 mK. We also predict the specific magnetic field dependence of the oscillatory energy levels of the pinned VAV state. The quantum-mechanical dynamics of a VAV pair can be used for quantum information processing. [1] M.V. Fistul et al., to appear in Phys.Rev.Lett. (cond-mat/0307705)