  The momentum distribution of Lambda^0 hyperons produced from the quark-gluon
plasma (QGP) in ultra-relativistic heavy-ion collisions is calculated in
dependence on their polarization. The momentum distribution of Lambda^0
hyperons is defined by matrix elements of relativistic quark Wigner operators,
which are calculated within the Effective quark model with chiral U(3)xU(3)
symmetry and the Quark-Gluon transport theory. We show that the polarization of
the Lambda^0 hyperon depends of the spin of the strange quark that agrees well
with the DeGrand-Miettinen model. We show that Lambda^0 hyperons, produced from
the QGP, are fully unpolarized. This means that a detection of unpolarized
Lambda^0 hyperons, produced in ultra-relativistic heavy-ion collisions, should
serve as one of the signatures for the existence of the QGP in intermediate
states of ultra-relativistic heavy-ion collisions.
