  Over the last decade there have been many advances in studies of quantum
walks (QWs) including a momentum-space QW recently realized in our spinor
Bose-Einstein condensate system. This QW possessed behaviors that generally
agreed with theoretical predictions; however, it also showed momentum
distributions that were not adequately explained by the theory. We present a
theoretical model which proves that the coherent dynamics of the spinor
condensate is sufficient to explain the experimental data without invoking the
presence of a thermal cloud of atoms as in the original theory. Our numerical
findings are supported by an analytical prediction for the momentum
distributions in the limit of zero-temperature condensates. This current model
provides more complete explanations to the momentum-space QWs that can be
applied to study quantum search algorithms and topological phases in
Floquet-driven systems.
