  The possibility of nonlocal quantum communication is considered. We
investigate three $gedankenexperiments$ that have variable entanglement: (1) a
4-detector polarization-entangled system, (2) a 4-detector path-entangled
system, and (3) a 3-detector path-entangled system that uses an innovative
optical mixer to combine photon paths. A new quantum paradox is reviewed in
which the presence or absence of an interference pattern in a path-entangled
two photon system, controlled by measurement choice, is a potential nonlocal
signal. We show that for the cases considered, even when interference patterns
can be switched off and on, there is always a "signal" interference pattern and
an "anti-signal" interference pattern that mask any observable interference
when they are added, even when entanglement and coherence are simultaneously
present. This behavior can be attributed to what in the literature has been
called "the complementarity of one- and two-particle interference".
