Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 8: Posters Transport

TT 8.41: Poster

Freitag, 4. März 2005, 14:00–18:00, Poster TU C

Fabrication of superconducting qubit stuctures — •Georg Wild, Tobias Heimbeck, Heribert Knoglinger, Karl Madek, Matteo Mariantoni, Christian Probst, Achim Marx, and Rudolf Gross — Walther-Meissner-Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany

Solid state based quantum bits (qubits) promise to be producible using present day micro- and nanofabrication technologies thus allowing scalability up to systems comprising a large number of qubits. Superconducting qubits are advantageous because of the superconducting energy gap. Superconducting qubits based on Josephson junctions where the Josephson coupling energy is larger than the charging energy are usually called flux qubits. We are fabricating flux qubits with different designs based on Al/Al₂O₃ tunnel junctions. Measurements on various test structures (Josephson junctions, SQUIDs, qubits) help to analyze and further optimize the system parameters and to compare the different qubit variants. Flux qubits require an external magnetic field bias generating half a flux quantum in the ring defining the qubit to reach the degeneracy point. To shift this degeneracy point to zero field a π-shift element has to be inserted into the ring. We have started to develop a process to fabricate π-shifters based on superconductor/ferromagnet/superconductor Josephson junctions where a thin ferromagnetic NiPd layer is embedded between two Nb layers. This work was supported by the Sonderforschungsbereich 631 of the Deutsche Forschungsgemeinschaft.