DC-SQUIDs (SQUID: Superconducting QUantum Interference Device) are investigated for their usability as phase quantum bits (qubits) within the EU-project "EuroSQIP" in cooperation with the CNRS in Grenoble. In collaboration with our partners at the CNRS an optimized SQUID circuit was designed, including a high frequency supply and filter structures. The SQUID circuits were fabricated from Nb/AlOx/Nb trilayers at PTB, using electron beam lithography, reactive ion etching and chemical-mechanical polishing of an SiO2 insulating layer. After a first examination of the SQUID structures at 4,2 K, some appropriate circuits were selected and characterized in detail in a dilution refrigerator at mK temperatures in Grenoble. The measurements demonstrated that the DC-SQUID can be operated as a qubit, i.e. as a two level quantum system. The SQUIDs showed a coherence time of Rabi-oscillations which is typical for phase qubits. The results demonstrate...
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