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SYQI: Quantum information processing in condensed media

SYQI 3: Poster

SYQI 3.3: Poster

Wednesday, March 26, 2003, 14:30–19:00, P2d

Observation of quantum tunneling of a Josephson vortex — •Andreas Wallraff¹, Jürgen Lisenfeld², Alexandr Lukashenko², Yuri Koval², Misha Fistul², and Alexey Ustinov² — ¹Department of Applied Physics / University of Yale, New Haven — ²Physikalisches Institut III / Universität Erlangen

We present first experimental observation of the macroscopic quantum tunneling of a single Josephson vortex through a magnetic-field controlled potential barrier in a long Josephson junction. The cross-over from thermal activation to quantum tunneling is observed in measurements of the vortex depinning current distribution when decreasing temperature. The quantized energy levels of the vortex in the well are observed spectroscopically by applying microwaves. The level separation scales with magnetic field and bias current as expected. The measured cross-over temperature is consistent with the theoretical prediction evaluated using the measured level separation. In the proposed vortex qubit two spatially distinct states of a quantum vortex in a double well potential can to be used to encode quantum information.