M. Merkli, I.M. Sigal, G.P. Berman
Resonance Theory of Decoherence and Thermalization
(528K, pdf)

ABSTRACT.  We present a rigorous analysis of the phenomenon of decoherence 
for general $N-$level systems coupled to reservoirs. The 
latter are described by free massless bosonic fields. We apply our 
general results to the specific cases of the qubit and the quantum 
register. We compare our results with the explicitly solvable case 
of systems whose interaction with the environment does not allow for 
energy exchange (non-demolition, or energy conserving interactions). We suggest a new approach which applies to a wide variety of systems which are not explicitly solvable.