Regensburg 2004 – scientific programme
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TT: Tiefe Temperaturen
TT 29: Quantenkoh
ärenz und Quanteninformationssysteme II
TT 29.14: Talk
Thursday, March 11, 2004, 18:00–18:15, H19
Numerical Renormalization Group for Quantum Two-Level Systems in a Dissipative Environment — •Ralf Bulla1, Matthias Vojta2, and Ning-Hua Tong1 — 1Theoretische Physik III, Universität Augsburg — 2Institut für Theorie der Kondensierten Materie, Universität Karlsruhe
The dynamics of quantum two-level systems has recently attracted a lot of interest in the context of quantum computing. The coupling to the environment strongly influences the phase coherence necessary to perform elementary quantum computing steps. A suitable description of the coupling of the qubit to the environment is given by the spin-boson model for which a reliable and (in particular) non-perturbative method is required; such a method should be applicable to general bath spectral functions (such as the sub-ohmic case with exponents of the bath spectral function s<1). Here we present the recently developed bosonic numerical renormalization group approach [R. Bulla, N. Tong, and M. Vojta, Phys. Rev. Lett. 91, 170601 (2003)]. In particular, we discuss the phase diagram of the spin-boson model for arbitrary exponents s and couplings α, as well as the dynamics across the whole phase diagram. Further applications of this approach (two coupled qubits, qubits coupling to a structured bath) are discussed.