  The complete density matrix for all polarization configurations in the
process B--> t tbar, where B is an off--shell Z or photon and t is the top
quark, is calculated numerically including oneloop QCD corrections, i.e.
virtual and real gluon contributions in O(alphas). The analysis is done in the
framework of the helicity formalism. The results are particularly suited for
top quark production at the Linear Collider, but may be useful in other
circumstances as well. Relations to LEP and Tevatron physics are pointed out.
