Regensburg 2004 – scientific programme

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TT: Tiefe Temperaturen

TT 22: Quantenkoh
ärenz und Quanteninformationssysteme I

TT 22.6: Talk

Wednesday, March 10, 2004, 15:45–16:00, H19

Dynamics of the spin-boson model with a structured environment — •Michael Thorwart¹, Elisabetta Paladino², and Milena Grifoni³ — ¹Institut für Theoretische Physik IV, Heinrich-Heine-Universität Düsseldorf — ²Dipartimento Metodologie Fisiche e Chimiche per L’ingegneria, Universitá di Catania, Italy — ³Institut für Theoretische Physik, Universität Regensburg

We investigate the dynamics of the spin-boson model when the spectral density of the bath shows a resonance at a characteristic frequency Ω but behaves Ohmically at small frequencies. A useful exact mapping of this system to a system composed of a quantum two-state system (TSS) coupled to an Ohmically damped harmonic oscillator (HO) with frequency Ω is invoked. The dynamics is calculated by employing the numerically exact quasiadiabatic path-integral technique. We find significant new properties compared to the Ohmic spin-boson model. By reducing the combined TSS+HO-system in the dressed states picture to a three-level system, we calculate analytically the dephasing rates for the special case at resonance. Finally, we apply our model to experimentally realized superconducting flux qubits coupled to an underdamped ds-SQUID-detector.