Coupled Harmonic Systems as Quantum Buses in Thermal Environments
  In this work, we perform a careful study of an special arrangement of coupled systems that consists of two external harmonic oscillators weakly coupled to an arbitrary network (data bus) of strongly interacting oscillators. Our aim is to establish simple effective Hamiltonians and Liouvillians allowing an accurate description of the dynamics of the external oscillators regardless the topology of the network. By simple we mean an effective description using just a few degrees of freedom. In order to do that, we employed the machinery of symplectic formalism to generalize and expand the ideas presented in [1], where the specific case of an isolated (no thermal baths) chain is treated. With the methodology developed here, we are able to treat general topologies and, under certain structural conditions, to also include the interaction with external environments. In order to illustrate the predictability of the simplified dynamics, we present a comparative study with the predictions of the numerically obtained exact description in the context of propagation of energy through the network. 
F. Nicacio and F.L. Semi\~ao
quant-ph