  A misunderstanding of entangled states has spawned decades of concern about
quantum measurements and a plethora of quantum interpretations. The
"measurement state" or "Schrodinger's cat state" of a superposed quantum system
and its detector is nonlocally entangled, suggesting that we turn to
nonlocality experiments for insight into measurements. By studying the full
range of superposition phases, these experiments show precisely what the
measurement state does and does not superpose. These experiments reveal that
the measurement state is not, as had been supposed, a paradoxical superposition
of detector states. It is instead a nonparadoxical superposition of two
correlations between detector states and system states. In this way, the
experimental results resolve the problem of definite outcomes ("Schrodinger's
cat"), leading to a resolution of the measurement problem. However, this
argument does not yet resolve the measurement problem because it is based on
the results of experiments, while measurement is a theoretical problem: How can
standard quantum theory explain the definite outcomes seen experimentally?
Thus, we summarize the nonlocality experiments' supporting theory, which
rigorously predicts the experimental results directly from optical paths.
Several previous theoretical analyses of the measurement problem have relied on
the reduced density operators derived from the measurement state, but these
solutions have been rejected due to criticism of reduced density operators.
Because it avoids reduced density operators, the optical-path analysis is
immune to such criticism.
