title: Flux-dependent crossover between quantum and classical behavior in a dc SQUID.
abstract: In a coupled system of one classical and one quantum mechanical degree of freedom, the quantum degree of freedom can facilitate the escape of the whole system. Such unusual escape characteristics have been theoretically predicted as the "Münchhausen effect." We implement such a system by shunting one of the two junctions of a dc SQUID with an additional capacitance. In our experiments, we detect a crossover between quantum and classical escape processes related to the direction of escape. We find that, under varying external magnetic flux, macroscopic quantum tunneling periodically alternates with thermally activated escape, a hallmark of the "Münchhausen effect."
authors.affiliation: Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Butz
authors.affiliation: Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
authors.forename: A K
authors.initials: AK
authors.lastname: Feofanov
authors.affiliation: Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany and National University of Science and Technology MISIS, Moscow 119049, Russia.
authors.forename: K G
authors.initials: KG
authors.lastname: Fedorov
authors.affiliation: Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Rotzinger
authors.affiliation: Theoretische Physik, ETH Zurich, 8093 Zürich, Switzerland.
authors.forename: A U
authors.initials: AU
authors.lastname: Thomann
authors.affiliation: Physikalisch Technische Bundesanstalt, 38116 Braunschweig, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Mackrodt
authors.affiliation: Physikalisch Technische Bundesanstalt, 38116 Braunschweig, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Dolata
authors.affiliation: Theoretische Physik, ETH Zurich, 8093 Zürich, Switzerland.
authors.forename: V B
authors.initials: VB
authors.lastname: Geshkenbein
authors.affiliation: Theoretische Physik, ETH Zurich, 8093 Zürich, Switzerland.
authors.forename: G
authors.initials: G
authors.lastname: Blatter
authors.affiliation: Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany and National University of Science and Technology MISIS, Moscow 119049, Russia and Russian Quantum Center, 100 Novaya, Skolkovo, Moscow Region 143025, Russia.
authors.forename: A V
authors.initials: AV
authors.lastname: Ustinov