Berlin 2024 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 18: Superconductivity: Poster
TT 18.46: Poster
Monday, March 18, 2024, 15:00–18:00, Poster C
Recent insights into the low frequency excess flux noise in superconducting quantum devices — •Anna Ferring-Siebert1, Fabian Kaap2, David Mazibrada1, Lukas Münch1, Andreas Fleischmann1, Christian Enss1, and Sebastian Kempf3,4,1 — 1KIP, Im Neuenheimer Feld 227, 69120 Heidelberg, Germany. — 2currently at PTB, Bundesallee 100, 38116 Braunschweig, Germany. — 3IMS, KIT, Hertzstraße 16, 76187 Karlsruhe, Germany. — 4IPE, KIT, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany.
In many applications low frequency excess flux noise (EFN), with a frequency dependence of 1/fα, limits the performance of superconducting quantum devices such as SQUIDs and Qubits. Although it was long believed that its magnitude expressed in units of magnetic flux SΦ(1 Hz) and exponent α are fairly independent of the device material and inductance, there meanwhile exist hints for the contrary. It is also known that EFN can depend on the equipment used for device fabrication, the reason for that however remained unknown up to now.
In this contribution, we discuss origins of fabrication induced EFN and means to minimize it. We show that material layers deposited with commercial deposition equipment can contain magnetic impurities causing EFN. We also present how we have modified commercial sputtering sources to reduce EFN. Finally, measurements investigating the dependence of EFN on device inductance and material choice are discussed.
Keywords: SQUID; low-frequency; noise; quantum device