AQC 2016 - Origin and Suppression of 1/f Magnetic Flux Noise

A Google TechTalk, June 28, 2016, presented by Robert McDermott (University of Wisconsin - Madison) ABSTRACT: Magnetic flux noise is a dominant source of dephasing and energy relaxation in superconducting qubits. The noise power spectral density varies with frequency as 1/f and spans 13 orders of magnitude. Recent work indicates that the noise is from unpaired magnetic defects on the surfaces of the superconducting devices. Here, we demonstrate that adsorbed molecular oxygen is the dominant contributor to magnetism in superconducting thin films. We show that this magnetism can be suppressed by appropriate surface treatment or improvement in the sample vacuum environment. We observe a suppression of static spin susceptibility by more than an order of magnitude, and a suppression of 1/f magnetic flux noise power spectral density by more than a factor of 5. These advances open the door to realization of superconducting qubits with improved quantum coherence. P. Kumar, U. Wisconsin, S. Sendelbach, U. Wisconsin, M. A. Beck, U. Wisconsin, J. W. Freeland, Argonne Natl. Lab, Z. Wang, UC-Irvine, H. Wang, UC-Irvine, C. C. Yu, UC-Irvine, R. Q. Wu, UC-Irvine, D. P. Pappas, NIST Boulder Presented at the Adiabatic Quantum Computing Conference, June 26-29, 2016, at Google's Los Angeles office.