  Theory and experiment both demonstrate that an entangled quantum state of two
subsystems is neither a superposition of states of its subsystems nor a
superposition of composite states but rather a coherent superposition of
nonlocal correlations between incoherently mixed local states of the two
subsystems. Thus, even if one subsystem happens to be macroscopic as in the
entangled "Schrodinger's cat" state resulting from an ideal measurement, this
state is not the paradoxical macroscopic superposition it is generally presumed
to be. It is, instead, a "macroscopic correlation," a coherent quantum
correlation in which one of the two correlated sub-systems happens to be
macroscopic. This clarifies the physical meaning of entanglement: When a
superposed quantum system A is unitarily entangled with a second quantum system
B, the coherence of the original superposition of different states of A is
transferred to different correlations between states of A and B, so the
entangled state becomes a superposition of correlations rather than a
superposition of states. This transfer preserves unitary evolution while
permitting B to be macroscopic without entailing a macroscopic superposition.
This resolves the "problem of outcomes" but is not a complete resolution of the
measurement problem because the entangled state is still reversible.
