Pointer Basis, and Inhibition of Quantum Tunneling by Environment-Induced Superselection

The purpose of this paper is to explore the idea that classical behavior can be forced upon a quantum system by a measurement-like coupling with its quantum environment. An example where such a mechanism of environment induced superselection is operating in competition with a hamiltonian evolution which in an isolated system would result in coherent quantum superpositions is afforded by recent discussions of macroscopic quantum coherence and tunneling. The possibility of existence of nonseparable correlations between macroscopic quantum observables in two different SQUIDs is raised.