Dresden 2006 – wissenschaftliches Programm
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TT: Tiefe Temperaturen
TT 32: Transport: Quantum Coherence and Quantum Information Systems - Part 2
TT 32.11: Vortrag
Donnerstag, 30. März 2006, 16:45–17:00, HSZ 304
Quantum tunneling of semifluxons in 0-π-0 long Josephson junction: Theory — •Edward Goldobin1, Karl Vogel2, Oliver Crasser2, Reinhold Walser2, Wolfgang Schleich2, Dieter Koelle1, and Reinhold Kleiner1 — 1Universität Tübingen, Physikalisches Institut - Experimentalphysik II, Auf der Morgenstelle 14, D-72076, Tübingen, Germany — 2Universität Ulm, Abteilung Quantenphysik, D-89069 Ulm, Germany
We consider a system of two semifluxons of opposite polarity in a 0-π-0 long Josephson junction, which classically can be in one of two degenerate states: ↑↓ or ↓↑. When the distance a between the 0-π boundaries (semifluxon’s centers) is a bit larger than the crossover distance ac, the system can switch from one state to the other due to thermal fluctuations or due to quantum tunneling. We map this problem to the dynamics of a single particle in a double well potential and estimate parameters for which quantum effects emerge. We also determine the classical-to-quantum crossover temperature as well as the tunneling rate (energy level splitting) between the states ↑↓ and ↓↑. This system may be a promising candidate for realization of qubits since semifluxons represent the ground state of the system. See [1] for details.
[1] Phys. Rev. B. 72, 054527 (2005).