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Regensburg 2019 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 40: Superconductivity: Qubits 1

TT 40.10: Vortrag

Mittwoch, 3. April 2019, 12:00–12:15, H48

Low frequency excess flux noise in dc-SQUIDs — •Anna Ferring, Andreas Fleischmann, Christian Enss, and Sebastian Kempf — 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. Recent experiments strongly hint for surface adsorbates as an origin of this noise contribution. But even though more and more information on its origin and physical properties are gathered, a lot of open questions remain such as whether additional sources of low frequency excess flux noise exist.

In this contribution, we show indications for a correlation between the noise amplitude of dc-SQUIDs and the dc-magnetization of material layers used for device fabrication. This suggests that low-frequency excess flux noise is to some extend caused by the conditions of the fabrication process. We further present a SQUID setup which allows for temperature dependent cross-correlation measurements of the magnetic flux noise of a sample SQUID. Finally, we discuss the scaling of low frequency excess flux noise of simple washer SQUIDs with device inductance showing that the energy sensitivity rather than the magnetic flux noise is the more appropriate figure of merit for describing low frequency excess flux noise.

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