title: Direct Identification of Dilute Surface Spins on Al_{2}O_{3}: Origin of Flux Noise in Quantum Circuits.
abstract: An on-chip electron spin resonance technique is applied to reveal the nature and origin of surface spins on Al_{2}O_{3}. We measure a spin density of 2.2×10^{17}  spins/m^{2}, attributed to physisorbed atomic hydrogen and S=1/2 electron spin states on the surface. This is direct evidence for the nature of spins responsible for flux noise in quantum circuits, which has been an issue of interest for several decades. Our findings open up a new approach to the identification and controlled reduction of paramagnetic sources of noise and decoherence in superconducting quantum devices.
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, United Kingdom.
authors.forename: S E
authors.initials: SE
authors.lastname: de Graaf
authors.affiliation: Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
authors.forename: A A
authors.initials: AA
authors.lastname: Adamyan
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Lindström
authors.affiliation: Institute of Chemical Physics, University of Latvia, LV 1586, Latvia.
authors.forename: D
authors.initials: D
authors.lastname: Erts
authors.affiliation: Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
authors.forename: S E
authors.initials: SE
authors.lastname: Kubatkin
authors.affiliation: National Physical Laboratory, Hampton Road, Teddington, TW11 0LW, United Kingdom.|Royal Holloway, University of London, Egham, TW20 0EX, United Kingdom.
authors.forename: A Ya
authors.initials: AY
authors.lastname: Tzalenchuk
authors.affiliation: Department of Microtechnology and Nanoscience, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
authors.forename: A V
authors.initials: AV
authors.lastname: Danilov