  We use a fiber based double slit Young interferometer for studying the
far-field spatial distribution of the two-photon coincidence rate (coincidence
pattern) for various quantum states with different degree of spatial
entanglement. The realized experimental approach allows to characterize
coincidence patterns for different states without any modifications of the
setup. Measurements were carried out with path-entangled and separable states.
The dependence of the coincidence pattern on the phase of the interferometer
for superposition and separable states was studied. The results have
implications for using of nonclassical light in multiphoton imaging, quantum
lithography, and studies of phase decoherence.
