All the statistical one-particle properties of entangled states can be anal
yzed using the reduced density matrix of the system. We present its evaluat
ion in the gedanken two-particle two-slit experiment. The method presented
here improves the mathematical analysis of the experiment, which is fundame
ntal in the understanding of the rules to sum probabilities in two-particle
interferometry. (C) 2000 Elsevier Science B.V. All rights reserved.