Majorana signatures in charge transport through a topological superconducting double-island system

We investigate the dynamics of a charge qubit consisting of two Coulomb-blockaded islands hosting Majorana zero modes. The frequency of the qubit is determined by coherent single-electron tunneling between two islands originating from the hybridization of two Majorana zero modes localized at the junction. We calculate the sequential tunneling current $I$ through the double-island device coupled to normal metal leads. We demonstrate that the $I\text{\ensuremath{-}}V$ characteristics in the large-bias regime can be used as a measurement of the coherent Majorana coupling ${E}_M$. We propose dc and ac transport experiments for measuring ${E}_M$, and discuss their limitations due to intrinsic dephasing mechanisms such as excited quasiparticles.