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TT: Fachverband Tiefe Temperaturen
TT 22: Superconductivity – Poster I
TT 22.7: Poster
Montag, 9. März 2026, 18:00–20:00, P1
Towards new precision measurements of the AC Josephson effect — •Sandip Saha1, Oliver Kieler1, Ralf Behr1, Jörn Beyer2, Johannes Kohlmann1, and Mark Bieler1 — 1Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany — 2Physikalisch-Technische Bundesanstalt (PTB), Abbestraße 2-12, 10587 Berlin, Germany
The AC Josephson effect is used today to realise the unit volt since it establishes a perfect relationship between voltage and frequency just based upon the magnetic flux quantum φ0=h/2e. Around four decades ago, the universality of the Josephson effect was studied and experimentally verified with an uncertainty of 3 parts in 1019 [1]. Considering the recent progress in superconducting quantum technology and metrology, we believe that re-evaluating this uncertainty could shed new light on the precision of the AC Josephson effect. We plan to use two independent Josephson junction arrays comprising several thousand Josephson junctions, being driven by a microwave generator to synthesize DC voltages. To detect small voltage differences between these two arrays, which will be connected in a superconducting loop, a state-of-the-art DC SQUID will be inductively coupled and used as an extremely sensitive null detector. At the conference, we will explain the principle behind our experimental setup, provide a detailed introduction of the involved quantum devices, which will be fabricated using the established Nb thin film technology at PTB, and present a roadmap for the upcoming measurements.
[1] https://doi.org/10.1103/PhysRevLett.58.1165
Keywords: superconductivity; Josephson junction; voltage standards; precision measurements; SQUID