Dresden 2006 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

TT: Tiefe Temperaturen

TT 32: Transport: Quantum Coherence and Quantum Information Systems - Part 2

TT 32.7: Vortrag

Donnerstag, 30. März 2006, 15:30–15:45, HSZ 304

Microshort induced pinning potential for a Josephson vortex, probed in the quantum limit with microwave spectroscopy. — •Astria Price, Alexander Kemp, and Alexey V. Ustinov — Physikalisches Institut III, Universitaet Erlangen-Nuernberg, Erlangen D-91058, Germany

A long annular Josephson junction with a lithographic microshort, produced by widening a short section of the junction, constitutes a vortex qubit candidate in which the height of the microshort induced potential barrier seen by a Josephson vortex is tuned via an applied magnetic field. We investigate the energy level structure of the vortex potential in this type of junction by means of microwave spectroscopy, and compare the results to a model based on the one-dimensional sine-Gordon equation. Applying bias current creates a metastable state for the vortex, in which it is pinned by either the magnetic field or the microshort, and escapes via thermal activation or quantum tunnelling. We measure the energy level separation between the ground and first excited states of the vortex in both types of metastable potential well, and extract the cross-over temperature from thermal activation to quantum tunnelling as a function of bias current and magnetic field strength.