  Coupling Majorana fermion excitations to coherent external fields is an
important stage towards their manipulation and detection. We analyse the charge
and transmon regimes of a topological nano-wire embedded within a
Cooper-Pair-Box, where the superconducting phase difference is coupled to the
zero energy parity states that arise from Majorana quasi-particles. We show
that at special gate bias points, the photon-qubit coupling can be switched off
via quantum interference, and in other points it is exponentially dependent on
the control parameter $E_J/E_C$. As well as a probe for
topological-superconductor excitations, we propose that this type of device
could be used to realise a tunable high coherence four-level system in the
superconducting circuits architecture.
