  We elaborate on a model of quantum random walk proposed by Hillery et. al.,
and Jeong et. al., which uses the multiports for quantum "coin tossing". The
dynamics of this model is analyzed for the case when the multiports are
arranged on the hypercube. If the hypercube is attached to semi-infinite lines,
then it can act as a scattering potential, which can be reduced to a quantum
walk on the line with non-unitary evolution. We also show how this model can be
implemented using simple quantum gates.
