Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 8: Posters Transport

TT 8.44: Poster

Friday, March 4, 2005, 14:00–18:00, Poster TU C

Probing superconducting phase qubits — •Jürgen A. Lisenfeld, Christian Coqui, Alexander Lukashenko, Alexander Kemp, Abdufarrukh A. Abdumalikov, and Alexey V. Ustinov — Physikalisches Institut III, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany

Solid-state quantum bits based on current-biased Josephson junctions have recently been shown as very promising. They require appropriate galvanic isolation of the junctions from the bias leads which can be achieved by the use of superconducting transformers. The resulting rf-SQUID has a double-well potential, where the discrete quantum levels in one well can be used as qubit states. State-dependent tunnelling to the other well changes the magnetic flux in the qubit, which is measured by a dc-SQUID. In current experiments, we investigate the operation of such qubits. Another crucial point is the coupling of qubits, which we study in a system of two capacitively coupled current-biased junctions. One effect which appears here is phase-locking, resulting in the formation of voltage steps in the current-voltage characteristics. Another feature of the coupled system is the appearance of entangled macroscopic quantum states, which we try to observe by using microwave spectroscopy.