Enhancing the spin-photon coupling with a micromagnet

TL;DR

This paper proposes a technique to significantly enhance the coupling between a solid-state spin and microwave photons in a superconducting cavity using a micromagnet, enabling stronger quantum interactions.

Contribution

The paper introduces a simple method to achieve strong spin-photon coupling via a micromagnet, greatly increasing coupling strength at the single spin level.

Findings

Coupling strength can be increased by up to four orders of magnitude.

Strong coupling is achieved through virtual magnonic excitations.

Potential applications in quantum information processing.

Abstract

Hybrid quantum systems involving solid-state spins and superconducting microwave cavities play a crucial role in quantum science and technology, but improving the spin-photon coupling at the single quantum level remains challenging in such systems. Here, we propose a simple technique to strongly couple a single solid-state spin to the microwave photons in a superconducting coplanar waveguide (CPW) cavity via a magnetic microsphere. We show that, strong coupling at the single spin level can be realized by virtual magnonic excitations of a nearby micromagnet. The spin-photon coupling strength can be enhanced up to typically four orders of magnitude larger than that without the use of the micromagnet. This work can find applications in quantum information processing with strongly coupled solid-state spin-photonic systems.