  The characterization of quantum correlations is crucial to the development of
new quantum technologies and to understand how dramatically quantum theory
departs from classical physics. Here we systematically study single- and
multiparticle interference patterns produced by general two- and three-qubit
systems. From this we establish on phenomenological grounds a new type of
quantum correlation for these systems, which we name quantum interference,
deriving some quantifiers that are given explicitly in terms of the density
matrix elements of the complete system. By using these quantifiers, we show
that, contrary to our expectations, entanglement is not a required property for
a composite quantum system to manifest multiparticle interference.
