  Topological superconductors are prime candidates for the implementation of
topological-quantum-computation ideas because they can support non-Abelian
excitations like Majorana fermions. We go beyond the low-energy effective-model
descriptions of Majorana bound states (MBSs), to derive non-equilibrium
transport properties of wire geometries of these systems in the presence of
arbitrarily large applied voltages. Our approach involves quantum Langevin
equations and non-equilibrium Green's functions. By virtue of a full
microscopic calculation we are able to model the tunnel coupling between the
superconducting wire and the metallic leads realistically; study the role of
high-energy non-topological excitations; predict how the behavior compares for
increasing number of odd vs. even number of sites; and study the evolution
across the topological quantum phase transition (QPT). We find that the
normalized spectral weight in the MBSs can be remarkably large and goes to zero
continuously at the topological QPT. Our results have concrete implications for
the experimental search and study of MBSs.
