Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 26: Transport - Poster Session

TT 26.24: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

Preparation and readout of bistable vortex states in a long annular Josephson junction containing a lithographic microshort. — •Alexander Kemp, Astria Price, and Alexey V. Ustinov — Physikalisches Institut III, Universitaet Erlangen-Nuernberg, Erlangen D-91058, Germany

We demonstrate classical state preparation and readout for a novel type of vortex qubit, in which a short section of the insulating barrier of a long annular Josephson junction is made slightly wider. This section of the junction acts like a microshort, where the height of the potential barrier so created can be tuned during experiment by varying the strength of an applied in-plane magnetic field. We develop a model for the double well potential, based on the one-dimensional sine-Gordon equation, in which the change in vortex rest mass energy due to the wider section of the junction is explicitly considered, and find the magnetic field dependence of the barrier height. Good agreement with measured vortex depinning currents from each well is obtained. The vortex was prepared in a given well by applying a series of “shaker” bias current pulses to the junction.