Fermion parity measurement and control in Majorana circuit quantum electrodynamics

TL;DR

This paper explores a topological superconducting circuit embedded in a microwave resonator, enabling the measurement and control of fermion parity states associated with Majorana fermions, with potential for enhanced qubit coherence.

Contribution

It develops an analytical framework for strong transmon-photon coupling and introduces protocols for initializing, controlling, and measuring Majorana fermion parity states in circuit QED.

Findings

Fermion parity can be detected via dispersive shifts in the optical cavity.

Parity eigenvalues are measurable in the strong-coupling regime.

Parity states can be coherently manipulated through second-order sideband transitions.

Abstract

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.