  Experimental evidence for Majorana bound states (MBSs) is so far mainly based
on the robustness of a zero-bias conductance peak. However, similar features
can also arise due to Andreev bound states (ABSs) localized at the end of an
island. We show that these two scenarios can be distinguished by an
interferometry experiment based on embedding a Coulomb-blockaded island into an
Aharonov-Bohm ring. For two ABSs, when the ground state is nearly degenerate,
cotunneling can change the state of the island and interference is suppressed.
By contrast, for two MBSs the ground state is nondegenerate and cotunneling has
to preserve the island state, which leads to $h / e$-periodic conductance
oscillations with magnetic flux. Such interference setups can be realized with
semiconducting nanowires or two-dimensional electron gases with
proximity-induced superconductivity and may also be a useful spectroscopic tool
for parity-flip mechanisms.
