Electrically Detected Interferometry of Majorana Fermions in a Topological Insulator

Majorana fermions are zero-energy quasiparticles that may exist in superconducting vortices and interfaces, but their detection is problematic since they have no charge. This is an obstacle to the realization of topological quantum computation, which relies on Majorana fermions to store qubits in a way which is insensitive to decoherence. We show how a pair of neutral Majorana fermions can be converted reversibly into a charged Dirac fermion. These two types of fermions are predicted to exist on the metallic surface of a topological insulator (such as ${\mathrm{Bi}}_2{\mathrm{Se}}_3$). Our Dirac-Majorana fermion converter enables electrical detection of a qubit by an interferometric measurement.