  In semiconductor-superconductor hybrid structures a topological phase
transition is expected as a function of chemical potential or magnetic field
strength. We show that signatures of this transition can be observed in
nonlinear Coulomb blockade transport through a ring shaped structure. In
particular, for a fixed electron parity of the ring, the flux periodicity of
the neutral excitation spectrum changes from the usual h/2e periodicity to a
characteristic h/e periodicity when tuning the system from the topologically
trivial to the nontrivial phase. We relate the h/e periodicity to the recently
predicted 4\pi periodicity of the Josephson current across a junction formed by
two topological superconductors.
