  We investigate the quantum electrodynamics of a device based on a topological
superconducting circuit embedded in a microwave resonator. The device stores
its quantum information in coherent superpositions of fermion parity states
originating from Majorana fermion hybridization. This generates a highly
isolated qubit whose coherence time could be greatly enhanced. We extend the
conventional semiclassical method and obtain analytical derivations for strong
transmon-photon coupling. Using this formalism, we develop protocols to
initialize, control, and measure the parity states. We show that, remarkably,
the parity eigenvalue can be detected via dispersive shifts of the optical
cavity in the strong-coupling regime and its state can be coherently
manipulated via a second-order sideband transition.
