SKM 2023 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 58: Poster: Superconductivity II

TT 58.15: Poster

Thursday, March 30, 2023, 15:00–18:00, P2/OG3

Superconducting flux qubits with stacked Josephson junctions — •Alex Kreuzer¹, Hossam Tohamy¹, Thilo Krumrey¹, Markus Griedel^1,2, Hannes Rotzinger^1,2, and Alexey V. Ustinov^1,2 — ¹Physikalisches Institut (PHI), Karlsruher Institut für Technologie (KIT) — ²Institut für Quantenmaterialien und -technologien (IQMT), Karlsruher Institut für Technologie (KIT)

Josephson junctions are often employed as nonlinear inductive elements in superconducting qubits as they allow to tailor specific circuit properties. The promising flux qubit types as fluxonium or quarton qubits require compact inductances which are often implemented as arrays of Josephson junctions. Here, the stray capacitance originating, for instance, from the capacitive coupling of an array island to ground, introduces the major limitation of this approach, since it introduces parasitic resonances at GHz frequencies which may degrade the overall qubit performance. We explore the possibility of implementing the qubit inductances by stacking Josephson junctions vertically and thus reducing the capacitance to ground. We present transport as well as microwave measurement data of stacked Josephson junctions and flux qubits made from them. Furthermore, we present a comparison of our experimental data with a detailed numerical simulation.