We present and demonstrate a method for balancing the two paths of a two-ph
oton interferometer of the Hong-Ou-Mandel (HOM) variety. This method remove
s the difficulties of balancing the paths in this type of interferometer wh
ere a type-I crystal is used for the generation of the entangled photon pai
rs. Using this method we show that we are consistently able to balance the
similar to 2000 mm path lengths in our HOM interferometer on average to wit
hin similar to 60 mu m. (C) 2000 American Institute of Physics. [S0034-6748
(00)01101-1].