Regensburg 2010 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 23: TR: Quantum Coherence and Quantum Information Systems 2

TT 23.2: Talk

Wednesday, March 24, 2010, 14:15–14:30, H18

Dissipative dynamics of driven quantum systems: a combined Floquet-Van-Vleck approach — •Johannes Hausinger, Carmen Vierheilig, and Milena Grifoni — Universität Regensburg, 93040 Regensburg, Germany

We investigate open quantum systems which are coupled to a classical, time-periodic field. Popular approximations to solve those time-dependent systems are the rotating wave approximation (RWA) and/or a perturbative expansion in the driving amplitude. In our work we combine Floquet theory with Van Vleck perturbation theory, which allows us to go beyond the RWA results and to arbitrary strong driving amplitudes, thus providing insight in so far not well explored parameter regimes. Environmental influences are accounted for by solving the Floquet-Bloch-Redfield master equation for the system’s dynamics.

Our approach can be applied for example to examine the behavior of qubits in the strong driving regime leading to so-called dressed states and multi-photon Rabi oscillations [1]. We solve the corresponding spin-boson problem and give analytical results for the renormalized Rabi frequency, dephasing and relaxation times of the qubit going beyond the known RWA and high-frequency results [2].

Further, we apply the above formalism to a driven qubit-detector system; i.e., we couple the qubit to a linear/nonlinear oscillator, which represents for example the read-out by a dc-SQUID and investigate the resulting modifications of the dissipative qubit dynamics.

[1] C. M. Wilson et al., Phys. Lett. 98, 257003 (2007)

[2] J. Hausinger, and M. Grifoni, arxiv:0910.0356 (2009)