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−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.