Tunable anisotropic quantum Rabi model via a magnon--spin-qubit ensemble

TL;DR

This paper proposes a hybrid quantum platform using a spin qubit coupled to a ferromagnet with squeezed magnons, enabling realization of the quantum Rabi model and generation of multi-qubit entangled states for quantum computing.

Contribution

It introduces a tunable anisotropic quantum Rabi model via a magnon--spin-qubit ensemble, enabling deep-strong coupling and multi-qubit entanglement generation.

Findings

Realizes the quantum Rabi model from isotropic to Jaynes-Cummings limit.

Achieves deep-strong coupling regime with controllable parameters.

Enables generation of GHZ states for quantum error correction.

Abstract

The ongoing rapid progress towards quantum technologies relies on new hybrid platforms optimized for specific quantum computation and communication tasks, and researchers are striving to achieve such platforms. We study theoretically a spin qubit exchange-coupled to an anisotropic ferromagnet that hosts magnons with a controllable degree of intrinsic squeezing. We find this system to physically realize the quantum Rabi model from the isotropic to the Jaynes-Cummings limit with coupling strengths that can reach the deep-strong regime. We demonstrate that the composite nature of the squeezed magnon enables concurrent excitation of three spin qubits coupled to the same magnet. Thus, three-qubit Greenberger-Horne-Zeilinger and related states needed for implementing Shor's quantum error-correction code can be robustly generated. Our analysis highlights some unique advantages offered by this hybrid platform, and we hope that it will motivate corresponding experimental efforts.