Berlin 2018 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 99: Poster Session: Transport

TT 99.48: Poster

Donnerstag, 15. März 2018, 15:00–19:00, Poster B

Low frequency excess flux noise in dc-SQUIDs — •A. Ferring, S. Kempf, and C. Enss — Kirchhoff-Institute for Physics, Heidelberg University, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany

Low frequency excess flux noise strongly impairs the performance of superconducting quantum devices (SQDs) such as SQUIDs and Qubits. It is, for example, the dominating mechanism causing decoherence in flux or phase Qubits and makes SQUID based measurements of low frequency signals rather challenging. But even though it has been extensively studied for many years, many open questions concerning its origin and properties remain. Recent experiments, for example, hint for surface adsorbates as a potential origin of noise contributions. It remains however unclear whether additional sources of low frequency excess flux noise exist. Therefore further investigations need to be done.

In this contribution, we first discuss a detailed study of low frequency excess flux noise in SQDs made of different materials like Nb, Al and PbIn, that hints for a material- and device-type dependence. We also show indications for a correlation between the 1/f-noise amplitude of dc-SQUIDs and the dc-magnetization of the used insulating SiO₂ layer originating from magnetic contaminations introduced during the actual fabrication process. Finally, we present noise measurements on dc-SQUIDs having all Nb/Al-AlO_x/Nb Josephson Junctions but using washers made from different materials.