title: Variable electrostatic transformer: controllable coupling of two charge qubits.
abstract: We propose and investigate a novel method for the controlled coupling of two Josephson charge qubits by means of a variable electrostatic transformer. The value of the coupling capacitance is given by the discretized curvature of the lowest energy band of a Josephson junction, which can be positive, negative, or zero. We calculate the charging diagram of the two-qubit system that reflects the transition from positive to negative through vanishing coupling. We also discuss how to implement a phase gate making use of the controllable coupling.
authors.affiliation: Department of Physics and Astronomy, University of Stony Brook, SUNY, Stony Brook, New York 11794-3800, USA.
authors.forename: D V
authors.initials: DV
authors.lastname: Averin
authors.forename: C
authors.initials: C
authors.lastname: Bruder