Engineering Entangled Coherent States of Magnons and Phonons via a Transmon Qubit

TL;DR

This paper proposes a hybrid quantum system architecture that uses a transmon qubit to generate and control entangled coherent states of magnons and phonons, enabling new quantum information processing possibilities.

Contribution

It introduces a novel scheme for creating and manipulating entangled coherent states of magnons and phonons using a superconducting transmon qubit coupled to magnetic and mechanical resonators.

Findings

High-fidelity generation of magnonic and mechanical Bell states.

Numerical validation including realistic dissipation effects.

A protocol for state readout using standard qubit operations.

Abstract

We propose a scheme for generating and controlling entangled coherent states (ECS) of magnons, i.e. the quanta of the collective spin excitations in magnetic systems, or phonons in mechanical resonators. The proposed hybrid circuit architecture comprises a superconducting transmon qubit coupled to a pair of magnonic Yttrium Iron Garnet (YIG) spherical resonators or mechanical beam resonators via flux-mediated interactions. Specifically, the coupling results from the magnetic/mechanical quantum fluctuations modulating the qubit inductor, formed by a superconducting quantum interference device (SQUID). We show that the resulting radiation-pressure interaction of the qubit with each mode, can be employed to generate maximally-entangled states of magnons or phonons. In addition, we numerically demonstrate a protocol for the preparation of magnonic and mechanical Bell states with high fidelity including realistic dissipation mechanisms. Furthermore, we have devised a scheme for reading out the prepared states using standard qubit control and resonator field displacements. Our work demonstrates an alternative platform for quantum information using ECS in hybrid magnonic and mechanical quantum networks.