  We demonstrate full selective control over the constructive or destructive
character of fourth-order recurring interferences in a modified version of a
HOM interferometer using comb-like two-photon states. The comb
spectral/temporal structure is obtained by inserting an etalon cavity in the
signal path of an entangled photon pair obtained by pulsed spontaneous
parametric down-conversion. Both a simple qualitative discussion and a complete
theoretical derivation are used to explain and analyze the experimental data.
