Phys. Rev. Lett. 103, 197001 (2009) [4 pages]Localization of Metal-Induced Gap States at the Metal-Insulator Interface: Origin of Flux Noise in SQUIDs and Superconducting QubitsReceived 21 July 2009; published 3 November 2009 The origin of magnetic flux noise in superconducting quantum interference devices with a power spectrum scaling as 1/f (f is frequency) has been a puzzle for over 20 years. This noise limits the decoherence time of superconducting qubits. A consensus has emerged that the noise arises from fluctuating spins of localized electrons with an areal density of 5×1017 m-2. We show that, in the presence of potential disorder at the metal-insulator interface, some of the metal-induced gap states become localized and produce local moments. A modest level of disorder yields the observed areal density. © 2009 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.103.197001
DOI:
10.1103/PhysRevLett.103.197001
PACS:
85.25.Dq, 03.67.Lx, 05.40.Ca, 73.20.Fz
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