Irreversible decay of nonlocal entanglement via a reservoir of a single degree of freedom

Recently, it has been realized that nonlocal disentanglement may take a finite time as opposite to the asymptotic decay of local coherences. We find in this paper that a sudden irreversible death of entanglement takes place in a two atom optical Stern-Gerlach model. In particular, the one degree nondissipative environment here considered suddenly destroys the initial entanglement of any Bell's states vertical bar {phi}{sup {+-}}> superposition.