Spin-State Selective Excitation in Spin Defects of Hexagonal Boron Nitride

TL;DR

This paper introduces a method for spin-state selective excitation in spin defects of hexagonal boron nitride using circularly polarized microwaves, improving control and sensitivity for quantum sensing applications.

Contribution

It demonstrates a novel technique for selective spin excitation in hBN defects via circularly polarized microwaves, enhancing quantum sensing capabilities.

Findings

Successful spin-selective excitation confirmed experimentally.

Use of circularly polarized microwaves enables control over specific spin transitions.

Technique improves magnetic sensitivity at low magnetic fields.

Abstract

Hexagonal boron nitride (hBN) has emerged as a promising two-dimensional platform for quantum sensing, due to its optically addressable spin defects, such as the negatively charged boron vacancy ($V_{\text{B}}^-$). Despite hBN being transferrable to close proximity to samples, spectral overlap of spin transitions due to large hyperfine interactions has limited its magnetic sensitivity. Here, we demonstrate spin-selective excitation of $V_{\text{B}}^-$ spin defects in hBN driven by circularly polarized microwave. Using a cross-shaped microwave resonance waveguide, we superimpose two orthogonally linearly polarized microwave shifted in phase from a RFSoC FPGA to generate circularly polarized microwaves. This enables selective spin $|0\rangle\rightarrow|-1\rangle$ or $|0\rangle\rightarrow|1\rangle$ excitation of $V_{\text{B}}^-$ defects, as confirmed by optically detected magnetic resonance experimentally and supported computationally. We also investigate the influence of magnetic field on spin-state selectivity. Our technique enhances the potential of hBN platform for quantum sensing through better spin state control and magnetic sensitivity particularly at low fields.