  We identify the quantum algebra of position and momentum operators for a
quantum system bearing an irreducible representation of the super Poincare
algebra in the N>1 and D=4 superspace both in the case where there are not
central charges in the algebra and when they are present. This algebra is
noncommutative for the position operators. We use the properties of
superprojectors acting on the superfields to construct explicit position and
momentum operators satisfying the algebra. They act on the projected wave
functions associated to the various supermultiplets with defined superspin
present in the representation. We show that the quantum algebra associated to
the massive superparticle appears in our construction and is described by a
supermultiplet of superspin 0. This result generalizes the construction for
D=4, N=1 reported recently. For the case N=2 with central charges we present
the equivalent results when the central charge and the mass are different. For
the kappa-symmetric case when these quantities are equal we discuss the
reduction to the physical degrees of freedom of the corresponding superparticle
and the construction of the associated quantum algebra.
