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/AlO_x/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/AlO_x/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.