Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 17: Postersitzung II: Transport, Quantenkoh
ärenz, Quantenflüssigkeiten

TT 17.23: Poster

Tuesday, March 9, 2004, 14:30–19:00, Poster A

Characterization of qubits based on current-biased Josephson junctions — •J. Lisenfeld¹, C. Coqui¹, A. Kemp¹, A. Lukashenko¹, A. Wallraff², and A.V. Ustinov¹ — ¹Physikalisches Institut III, Universität Erlangen-Nürnberg, 91058 Erlangen, Germany — ²Dept. Applied Physics, Yale University, New Haven, CT 06520, USA

The discrete energy levels of small current-biased Josephson junctions can be used as logical states for quantum computation [1]. Using microwave spectroscopy, we characterize both the level spacing and their dissipation-limited lifetimes. We report the observation of multi-photon transitions [2] between levels at photon energies being integer fractions of the transition energy, as it is expected for an anharmonic oscillator. For a capacitively coupled two-junction system, which we currently study, entangled macroscopic quantum states should be observable using the same technique. Our experimental results available to date will be presented.

[1] J.M. Martinis et. al., Phys. Rev. Lett. 89, 117901 (2002)

[2] A. Wallraff et. al., Phys. Rev. Lett. 90, 037003 (2003)