  When a quantum system is placed in thermal environments, we often assume that
the system relaxes to the Gibbs state in which decoherence takes place in the
system energy eigenbasis. However, when the coupling between the system and the
environments is strong, the stationary state is not necessarily the Gibbs state
due to environment-induced decoherence which can be interpreted as continuous
measurement by the environments. Based on the einselection proposed by Zurek,
we postulate that the Gibbs state is projected onto the pointer basis due to
the continuous measurement. We justify the proposition by exact numerical
simulation of a pair of coupled qubits interacting with boson gases.
Furthermore, we demonstrate that heat conduction in non-equilibrium steady
states can be suppressed in the strong coupling limit also by the
environment-induced decoherence.
