  A three-body quantum correlation is calculated for two particles reflecting
from a mirror. Correlated interference, a consequence of conservation of energy
and momentum, occurs for states in which the order of reflection is
indeterminate. The resulting quantum joint probability density function
exhibits interference with diverse characteristics, depending on the coherence
lengths of the substates. Marginal probability density functions can contain
information about the quantum nature of all three bodies, even if only one
particle is measured. Microscopic particles reflecting from a mesoscopic or
macroscopic mirror are used to illustrate unique features of this three-body
correlation interferometry. The microscopic momentum exchanged then generates
mirror substates which interfere to produce quantum effects which do not vanish
with increasing mirror mass, while the small displacement between these mirror
states can yield negligible environmental decoherence times.
