title: 1/f Flux noise in Josephson phase qubits.
abstract: We present a new method to measure 1/f noise in Josephson quantum bits (qubits) that yields low-frequency spectra below 1 Hz. A comparison of the noise taken at positive and negative bias of a phase qubit shows the dominant noise source to be flux noise and not junction critical-current noise, with a magnitude similar to that measured previously in other systems. Theoretical calculations show that the level of flux noise is not compatible with the standard model of noise from two-level state defects in the surface oxides of the films.
authors.affiliation: Department of Physics, University of California, Santa Barbara, California 93106, USA.
authors.forename: Radoslaw C
authors.initials: RC
authors.lastname: Bialczak
authors.forename: R
authors.initials: R
authors.lastname: McDermott
authors.forename: M
authors.initials: M
authors.lastname: Ansmann
authors.forename: M
authors.initials: M
authors.lastname: Hofheinz
authors.forename: N
authors.initials: N
authors.lastname: Katz
authors.forename: Erik
authors.initials: E
authors.lastname: Lucero
authors.forename: Matthew
authors.initials: M
authors.lastname: Neeley
authors.forename: A D
authors.initials: AD
authors.lastname: O'Connell
authors.forename: H
authors.initials: H
authors.lastname: Wang
authors.forename: A N
authors.initials: AN
authors.lastname: Cleland
authors.forename: John M
authors.initials: JM
authors.lastname: Martinis