the interaction of a Cooper pair box (CPB) with a nanomechanical resonator [17]. This system is given by: where E$_{C}$ and E$_{J}$ are the charging energy and the Josephson energy of the CPB, ω is the fundamental frequency of the resonator, and δn lies between − 1 / 2 and 1 / 2. At the degeneracy point δn = 0 this Hamiltonian can be written in the form of that of Eq. (1) under a similarity transformation, where we identify ω$_{0}$ = E$_{J}$ , g$_{ph}$ = 0, and g$_{r}$ = g$_{nr}$ = g . The similarity transformation is given by the operator e $^{iS$_{y}$}$, with S$_{y}$ being the y -projection of the spin operator. ¿From the symmetry of the Hamiltonian (12), one finds a DFS corresponding to the state c$_{+}$ = c$_{−}$ = 1 $_{/}$√$_{2 and}$ c$_{+}$ = − c$_{−}$ = 1 $_{/}$√$_{2. Hence, the value of}$ S$_{max}$ will always be unity for all values of g , irrespective of the values of A$_{+}$$_{−}$ . Nonetheless, overlapping resonances affect the decoherence in this system. Specifically, as A$_{+}$$_{−}$ increases with g , the variation of S with changes in the relative phase θ between c$_{±}$ also increases. This is shown in Fig. 5 where the difference S$_{diff}$ between the maximum and minimum values of S and the values of A$_{+}$$_{−}$ with g are seen to be strongly correlated. On the other hand, if g$_{r}$ = g$_{nr}$ , there is no DFS in the system. In that case, the results (not shown) behave similarly to, e.g., Fig. 2. That is, a plot of S$_{max}$ and A$_{±}$ as a function of g$_{r}$ , with g$_{r}$ = g$_{nr}$ and g$_{ph}$ = 0, shows a clear correlation between the maximum achievable value of S and the overlapping resonance contribution. We have introduced a new unifying approach to considering the resistance to decoherence of system superposition states. Specifically, using the generic class of spin-boson systems as an example we have shown that overlapping resonances of the system bare states, and the associated interference between these states, provide insight into the dependence of the deco- herence of system superposition states in the important regime of strong system-environment coupling. For example, within a given class of Hamiltonians, increasing overlapping reso- nances contributions allow for states of higher purity. The approach is completely general, although it has been applied here to a spin 1/2 particle interacting with a single thermal 10 V. SUMMARY H$_{CPB}$ = 4 E$_{C}$δnS$_{z}$ − ( E$_{J}$/ 2) S$_{x}$ + ℏ ωa $^{†}$a + ℏ gS$_{z}$ ( a + a $^{†}$) , (12)