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TT: Fachverband Tiefe Temperaturen
TT 34: TR: Quantum Coherence and Quantum Information Systems 2 (jointly with MA and HL)
TT 34.10: Vortrag
Mittwoch, 16. März 2011, 16:45–17:00, HSZ 03
Defect models in superconducting phase qubits — •Clemens Müller1,2, Jared H. Cole3,2, Pavel Bushev4,2, Grigorij J. Grabovskij4, Jürgen Lisenfeld4, Alexey V. Ustinov4,2, and Alexander Shnirman1,2 — 1Institut für Theorie der Kondensierten Materie, KIT, Karlsruhe, Germany — 2DFG Center for Functional Nanostructures (CFN), Karlsruhe, Germany — 3Institut für Theoretische Festkörperphysik, KIT, Karlsruhe, Germany — 4Physikalisches Institut, KIT, Karlsruhe, Germany
Superconducting qubits often show signatures of coherent coupling to intrinsic two-level systems (TLS), which manifest themselves as avoided level crossings in spectroscopic data. We use detailed theoretical models to determine the form of the coupling between a superconducting phase qubit and a TLS. Fitting the experimental data with our theoretical model allows us to determine all relevant system parameters. A strong qubit-defect coupling is observed, with a nearly vanishing longitudinal component. Using these estimates, we quantitatively compare several existing theoretical models for the microscopic origin of TLS.