Coherent single-electron transport in hybrid superconductor-semiconductor Coulomb islands*

The spatial separation of Majorana modes is expected to allow coherent transport of single electrons through a Coulomb blockaded one-dimensional topological superconductor [1]. Here we investigate phase coherent transport in a hybrid Al-InAs Coulomb island embedded in an Aharonov-Bohm interferometer. When a magnetic field is applied, the energy of a discrete sub-gap state is lowered below the charging energy and conductance oscillations are observed with a magnetic flux period of h/e (h is the Planck constant and e is the elementary charge), which indicates coherent transport of single electrons. The oscillation amplitude is maximized when the Coulomb peaks are 1 electron (1e) periodic, while the interference signal is suppressed when transport is 2e periodic or the island is in the normal state. The observation of phase-coherent transport enables us to investigate the coupling of Majorana modes from two separated topological wires with the goal of creating a topological qubit.

[1] Fu, L. Phys. Rev. Lett. 104, 056402 (2010)