Dresden 2006 – scientific programme

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TT: Tiefe Temperaturen

TT 7: Superconductivity & Solids At Low Temperature - Poster Session

TT 7.48: Poster

Monday, March 27, 2006, 14:00–17:45, P1

Fabrication and characterization of Al/AlO_x based superconducting flux-qubits — •Martin Goeppl, Sonia Dandl, Tobias Heimbeck, Karl Madek, Matteo Mariantoni, Georg Wild, 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 coupling energy larger than the charging energy are called flux qubits. The qubit states are given by a symmetric superposition of currents flowing clockwise and counter-clockwise when it is frustrated by applying a magnetic field corresponding to half a flux quantum in the loop. The system can be read out by a dc SQUID comprising the qubit.

We are fabricating flux qubits based on Al/AlO_x/Al tunnel junctions, using electron beam lithography and shadow evaporation technique. A crucial point was to establish and optimize the oxidation process for the lower electrode in order to fabricate Josephson junctions with well defined critical currents. Furthermore, the design of the electromagnetic environment is an important issue, which is required to isolate the qubit environmental sources of decoherence. Measurements on various test structures (Josephson junctions, SQUIDs, qubits) were used to analyze and further optimise the fabrication parameters.

This work is supported by the Sonderforschungsbereich 631 of the Deutsche Forschungsgemeinschaft