A two-photon interferometer without double-slits and without beam-splitters is presented. The frequency of the oscillations of the coincidence interference patterns is varied. These frequencies are associated to the single and to the two-photon wavepackets. Frequencies that are fractions and multiples of the single photon one are observed, in agreement with theory. These variable frequency oscillations are well understood in terms of the quantum theory and two particle entanglement. Some applications in the new field of quantum imaging and measurements of refraction indexes are promising possibilities. The interferomenter is being used in experiments for producing and manipulating entangled states. The entangled states are essential in the field of quantum information.