A survey of top quark polarization at a polarized linear e^+ e^- collider

We discuss in detail top quark polarization in above-threshold (t bar t)-production at a polarized linear e^+ e^- collider. We pay particular attention to the minimization and maximization of the polarization of the top quark by tuning the longitudinal polarization of the e^+ and e^- beams. The polarization of the top quark is calculated in full next-to-leading order QCD. We also discuss the beam polarization dependence of the longitudinal spin-spin correlations of the top and antitop quark spins.