Regensburg 2016 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 33: Superconductivity: Cryodedetectors & Cryotechnique

TT 33.3: Vortrag

Dienstag, 8. März 2016, 14:30–14:45, H19

Low-frequency excess flux noise in superconducting devices — •Sebastian Kempf, Anna Ferring, Andreas Fleischmann, and Christian Enss — Kirchhoff-Institute for Physics, Heidelberg University, Heidelberg, Germany.

Low-frequency noise is a rather universal phenomenon and appears in physical, chemical, biological or even economical systems. However, there is often very little known about the underlying processes leading to its occurrence. In particular, the origin of low-frequency excess flux noise in superconducting devices has been an unresolved puzzle for many decades. Its existence limits, for example, the coherence time of superconducting quantum bits or makes high-precision measurements of low-frequency signals using SQUIDs rather challenging. Recent experiments suggest that low-frequency excess flux noise in Josephson junction based devices might be caused by the random reversal of interacting spins in surface layer oxides and in the superconductor-substrate interface. Even if it turns out to be generally correct, the underlying physical processes, i.e. the origin of these spins, their physical nature as well as the interaction mechanisms, have not been resolved so far.

In this contribution we discuss recent measurements of low-frequency SQUID noise which we performed to investigate the origin of low-frequency excess flux noise in superconducting devices. Within this context we give an overview of our measurement techniques and link our data with present theoretical models and literature data.