Towards achieving strong coupling in 3D-cavity with solid state spin resonance

TL;DR

This paper presents innovative 3D microwave cavity designs that significantly enhance the coupling strength between microwave photons and solid-state spins, enabling advanced studies of strong coupling phenomena in quantum systems.

Contribution

The paper introduces a novel 3D cavity design with higher magnetic filling factor and cooperative factor, surpassing previous 1D superconducting cavities for NV center spin coupling.

Findings

Magnetic filling factor up to 4 times higher than previous designs

Achieved up to 200 times better cooperative factor with double-split resonator

Designs facilitate exploration of strong and ultra-strong coupling effects

Abstract

We investigate the microwave magnetic field confinement in several microwave 3D-cavities, using 3D finite-element analysis to determine the best design and achieve strong coupling between microwave resonant cavity photons and solid state spins. Specifically, we design cavities for achieving strong coupling of electromagnetic modes with an ensemble of nitrogen vacancy (NV) defects in diamond. We report here a novel and practical cavity design with a magnetic filling factor of up to 4 times (2 times higher collective coupling) than previously achieved using 1D superconducting cavities with small mode volume. In addition, we show that by using a double-split resonator cavity, it is possible to achieve up to 200 times better cooperative factor than the currently demonstrated with NV in diamond. These designs open up further opportunities for studying strong and ultra-strong coupling effects on spins in solids using alternative systems with a wider range of design parameters.