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Regensburg 2007 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 8: Superconductivity - Poster Session

TT 8.41: Poster

Monday, March 26, 2007, 14:00–17:45, Poster A

Fabrication of Josephson based superconducting quantum devices — •Tobias Heimbeck, Sonia Dandl, Achim Marx, and Rudolf Gross — Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, D-85748 Garching

Superconducting qubits based on superconducting loops containing an odd number of Josephson junctions with a Josephson coupling energy larger than the charging energy are called flux qubits. The qubit states are given by a symmetric superposition of states corresponding to clockwise and counter clockwise circulating currents at a flux bias of half a flux quantum. We have fabricated superconducting flux qubits based on Al/AlOx/Al tunnel junctions, using electron beam lithography and shadow evaporation technique. Junctions with areas down to 100×100 nm2 could be realized . A crucial point was to establish and optimize the oxidation process for the lower electrode as well as to design the electromagnetic environment by suitable shunting capacitors and resistors. We established a process allowing to fabricate on chip Al/AlOx/Al capacitors. Using either optical or electron beam lithography we realized capacitors with a specific capacitance of 14 fF/µm2. And resistance values well above 100 MΩ for capacitor areas up to 1000 µm2. These capacitors are suited as on chip shunting capacitors for flux qubits, isolating the qubits from environmental noise sources.

This work was supported by the DFG via SFB 631.

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