Overlapping resonances in the resistance of superposition states to decoherence

Overlapping resonances are shown to provide new insights into the extent of decoherence experienced by a system superposition state in the regime of strong system-environment coupling. As an example of this general approach, a generic system comprising spin-half particles interacting with a thermalized oscillator environment is considered. We find that (a) among the collection of parametrized Hamiltonians, the larger the overlapping resonances contribution, the greater the maximum possible purity, and (b) for a fixed Hamiltonian, the larger the overlapping resonances contribution, the larger the range of possible values of the purity as one varies the phases in the system superposition states. Systems displaying decoherence free subspaces show the largest overlapping resonances contribution. (C) 2010 American Institute of Physics. [doi:10.1063/1.3460262]