  The utilization and control of nonlocal quantum interactions is an area of
active investigation. This is not limited to subatomic structures but extends
to the macroscopic level. Nonlocal interactions can be from either entanglement
or path indistinguishability (the path integral for larger systems), with the
latter being further subdivided as discussed. These two distinct phenomenon
have recently been treated often in the literature as essentially identical,
which is problematic when utilizing them for practical applications. The
confusion may lie in misunderstanding the physics of the type II spontaneous
parameteric downconversion source (SPDS), which is used extensively with
entanglement studies. This paper examines the distinction, and why it is
important for practical applications, between quantum correlations from path
indistinguishability versus entanglement. The path indistinguishability
approaches discussed, under ambient conditions, are performed with a thermal
source or, a coherent source (single photon wavepacket) when local
entanglements in both arm have specific characteristics. The latter we will
show has the property that it can surprisingly lead to coherence expansion
rather than decoherence under the proper conditions. Nonlocal quantum
correlations are a complex topic that extends beyond quantum entanglement.
