Tunability of microwave transitions as a signature of coherent parity mixing effects in the Majorana-Transmon qubit

TL;DR

This paper explores how the coupling between Majorana fermions and microwave fields in a topological transmon can be controlled via quantum interference, enabling potential applications in quantum information processing.

Contribution

It introduces a method to tune the microwave transitions in a Majorana-Transmon qubit by exploiting quantum interference effects at specific gate biases.

Findings

Photon-qubit coupling can be turned off at special gate bias points.

Coupling strength depends exponentially on the ratio E_J/E_C.

Device can serve as a tunable, high-coherence four-level quantum system.

Abstract

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.