  We present a study on two-particle indistinguishability and particle-species
identification by introducing a Fisher-information (FI) approach---in which two
particles pass through a two-wave mixing operation and the number of particles
is counted in one of the output modes. In our study, we first show that FI can
reproduce the Hong-Ou-Mandel (HOM) effect with two bosons or two fermions. In
particular, it is found that even though bosons and fermions exhibit different
physical behavior (i.e., "bunching" or "anti-bunching") due to their
indistinguishability, the aspects of HOM-like dip are quantitatively same. We
then provide a simple method for estimating the degree of two-particle
indistinguishability in a Mach-Zehnder interferometer-type setup. The presented
method also enables us to identify whether the particles are bosons or
fermions. Our study will provide useful primitives for various study of boson
and fermion characteristics.
