Majorana qubit readout using longitudinal qubit-resonator interaction

We propose a quantum nondemolition Majorana qubit readout protocol based on parametric modulation of a longitudinal interaction between a pair of Majorana bound states and a resonator. The interaction can be modulated through microwave-frequency gate voltage or flux control of a tunable tunnel barrier. The qubit-resonator coupling is quantum nondemolition to exponential accuracy, a property inherited from the topological nature of the Majorana zero modes. The same mechanism as used for single-qubit readout can also be extended to perform multiqubit measurements and be used to enact long-range entangling gates.