Berlin 2024 – scientific programme
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QI: Fachverband Quanteninformation
QI 16: Superconducting Qubits (joint session QI/TT)
QI 16.3: Talk
Wednesday, March 20, 2024, 10:00–10:15, HFT-FT 131
Frequency tuning of superconducting qubits by junction annealing — •Julius Feigl1,2, Leon Koch1,2, Florian Wallner1,2, Niklas Bruckmoser1,2, David Bunch1,2, Lasse Södergren1,2, Christian Schneider1,2, and Stefan Filipp1,2 — 1Technical University of Munich, TUM School of Natural Sciences, Physics Department, Garching, Germany — 2Walther-Meißner-Institut, Bayerische Akademie der Wissenschaften, Garching, Germany
When scaling superconducting quantum processors beyond a couple of qubits, frequency collisions can become a limiting factor for gate fidelities. These collisions arise from parameter variations in the fabrication process, resulting in imprecise frequency targeting. A solution to enhance frequency targeting of individual superconducting qubits is the controlled annealing of the Josephson junction. In fact, Josephson junction resistance can be increased by local heating via a tightly focused laser beam. This leads to a modified Josephson inductance. In our work, we investigate wafer-scale laser annealing of fixed-frequency transmons with Al/AlOx/Al junctions. We explore the influence of annealing parameters on the resistance change for various junction sizes. The observed variations of the junction resistance after the annealing step reveal different temperature regimes for annealing. Temperatures exceeding 200 ∘C induce a reduction of up to 35 % in resistance, while temperatures below lead to an increase of up to 5 % in resistance. Consequently, we present a prospective approach to bi-directional annealing.
Keywords: Qubit fabrication; Frequency targeting; Josephson junction