title: Enhancement of macroscopic quantum tunneling by Landau-Zener transitions.
abstract: Motivated by recent realizations of qubits with a readout by macroscopic quantum tunneling in a Josephson junction, we study the problem of barrier penetration in the presence of coupling to a spin-1 / 2 system. It is shown that, when the diabatic potentials for fixed spin intersect in the barrier region, Landau-Zener transitions lead to an enhancement of the tunneling rate. The effect of these spin flips in imaginary time is in qualitative agreement with experimental observations.
authors.affiliation: Physikalisches Institut, Albert-Ludwigs-Universität Freiburg, Hermann-Herder-Strasse 3, D-79104 Freiburg, Germany. ankerhold@physik.uni-freiburg.de
authors.forename: Joachim
authors.initials: J
authors.lastname: Ankerhold
authors.forename: Hermann
authors.initials: H
authors.lastname: Grabert