Decoherence and relaxation of coupled qubits

Ulrich Weiss

University of Stuttgart, Institute of Theoretical Physics, Stuttgart, Germany

We study the reduced dynamics of two interacting spins or qubits, each coupled to its own environment. Employing functional integral methods, we derive the solution for the reduced density matrix in analytic form in the white-noise limit and analyze the rich behaviors in diverse limits ranging from weak interaction and/or low temperature to strong interaction and/or high temperature. We also view the one spin as being coupled to a spin-boson environment and consider the complementary regimes in which it is effectively nonlinear and in which it can be regarded as a resonant bosonic environment.