Image we create a superposition of states, say a|g> + b|e> with a relative phase between the coefficients (or amplitudes) a and b, at time 0, what will happen afterwards is that the superposition will be destroyed and one is left with a statistical mixture of states. This is the decoherence process originating from the inevitable interaction with the surrounding environment. That is to say, there is no closed system in Nature.
One possible strategy to control the decoherence process that we recently proposed is to vary the relative phase between a and b. Check the paper by Hu, Gu, and Franco for a comprehensive study of how this can be done in the context of electronic decoherence (g, e refer to electronic states) due to electron-nuclear couplings.