  Acausal features of quantum electrodynamic processes are discussed. While
these processes are not present for the classical electrodynamic theory, in the
quantum electrodynamic theory, acausal processes are well known to exist. For
example, any Feynman diagram with a ``loop'' in space-time describes a
``particle'' which may move forward in time or backward in time or in
space-like directions. The engineering problems involved in experimentally
testing such causality violations on a macroscopic scale are explored.
