title: Quantum dynamics in a camelback potential of a dc SQUID.
abstract: We investigate a quadratic-quartic anharmonic oscillator formed by a potential well between two potential barriers. We realize this novel potential with a dc SQUID at near-zero current bias and flux bias near half a flux quantum. Escape out of the central well can occur via tunneling through either of the two barriers. We find good agreement with a generalized double-path macroscopic quantum tunneling theory. We also demonstrate an "optimal line" in current and flux bias along which the oscillator, which can be operated as a phase qubit, is insensitive to decoherence due to low-frequency current fluctuations.
authors.affiliation: Institut Néel, C.N.R.S.-Université Joseph Fourier, BP 166, 38042 Grenoble-cedex 9, France.
authors.forename: E
authors.initials: E
authors.lastname: Hoskinson
authors.forename: F
authors.initials: F
authors.lastname: Lecocq
authors.forename: N
authors.initials: N
authors.lastname: Didier
authors.forename: A
authors.initials: A
authors.lastname: Fay
authors.forename: F W J
authors.initials: FW
authors.lastname: Hekking
authors.forename: W
authors.initials: W
authors.lastname: Guichard
authors.forename: O
authors.initials: O
authors.lastname: Buisson
authors.forename: R
authors.initials: R
authors.lastname: Dolata
authors.forename: B
authors.initials: B
authors.lastname: Mackrodt
authors.forename: A B
authors.initials: AB
authors.lastname: Zorin