Regensburg 2010 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 9: SC: Poster Session
TT 9.47: Poster
Montag, 22. März 2010, 14:00–18:00, Poster A
Experiments with phase qubits and two-level-fluctuators — •Grigorij J. Grabovskij, Pavel Bushev, Juergen Lisenfeld, Alexander Lukashenko, and Alexey V. Ustinov — KIT, Physikalisches Institut, Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe
We explore the complexity of the dynamical behaviour of a system consisting of a Josephson phase qubit and several two-level-fluctuators (TLF) coupled to it. Coherent driving of a qubit at the resonance with a TLF results in formation of a hybrid system consisting of 4 levels [1]. In our study we aim at a more detailed understanding of the physical nature of TLFs and their interaction with the qubit and electromagnetic environment. The presence of TLFs clearly appears in excitation spectrum of the qubit as avoided level crossings. The measured relaxation dynamics of individual TLFs yields the value for decay time T1 and decoherence time T2. Surprisingly, the measured T1 and T2 of some of TLFs exceed those of the qubit (∼ 100 ns). We show that quantum beating between qubit and TLF reveals the presence of weak fluctuators which are hardly detectable in a standard spectroscopy. We will report new data on swap-spectroscopy, in which a microwave pulse and population swap between qubit and fluctuator is followed by the qubit readout. Using this method, it becomes possible to study direct interaction of microwave excitation. [1] J. Lisenfeld et al., arXiv:0909.3425