  A modification of the standard Hong-Ou-Mandel interferometer is proposed
which allows one to replicate the celebrated coincidence dip in the case of
two-independent delay parameters. In the ideal case where such delays are
sufficiently stable with respect to the mean wavelength of the pump source,
properly symmetrized input bi-photon states allow one to pinpoint their values
through the identification of a zero in the coincidence counts, a feature that
cannot be simulated by semiclassical inputs having the same spectral
properties. Besides, in the presence of fluctuating parameters the zero in the
coincidences is washed away: still the bi-photon state permits to recover the
values of parameters with a visibility which is higher than the one allowed by
semiclassical sources. The detrimental role of loss and dispersion is also
analyzed and an application in the context of quantum positioning is presented.
