  The entangled "Schrodinger's cat state" of a quantum and its measurement
apparatus is not a paradoxical superposition of states but is instead a
non-paradoxical superposition of nonlocal coherent correlations between states:
An un-decayed nucleus is correlated with a live cat, and a decayed nucleus is
correlated with a dead cat. This elucidation of entanglement is demonstrated by
quantum-theoretical analysis and by experiments performed in 1990 using
entangled photon pairs. Thus the cat state does not predict a dead-and-alive
cat. Instead of indefinite superpositions, it predicts mixtures of definite
eigenvalues even though the subsystems are not actually in the corresponding
eigenstates, a situation that implies a (trivial) revision of the standard
eigenvalue-eigenstate rule. Because the subsystem states are not mixed even
though the subsystem eigenvalues are mixed, this analysis avoids two common
objections to such a resolution, namely improper density operators and basis
ambiguity. Thus, entanglement transfers coherence from the superposed quantum
to correlations between the quantum and its measuring apparatus, permitting
instantaneous collapse without interrupting the global unitary evolution. This
resolves a key part of the measurement problem.
