Sensors based on spin qubits in 2D crystals offer the prospect of nanoscale proximities between sensor and source, which could provide access to otherwise inaccessible signals. For AC magnetometry, the sensitivity and frequency range are typically limited by the noise spectrum, which determines the qubit coherence time. We address this using phase modulated continuous concatenated dynamic decoupling, which extends the coherence time towards the T₁ limit at room temperature and enables tuneable narrowband AC magnetometry. Using an ensemble of negatively charged boron vacancies in hexagonal boron nitride, we detect out-of-plane AC fields in the range of ~ 10 − 150 MHz, and in-plane fields within ± 150 MHz of the electron spin resonance. We measure an AC magnetic field sensitivity of \(\sim 1\,\mu {{{\rm{T}}}}/\sqrt{{{{\rm{Hz}}}}}\) at ~ 2.5 GHz, for a sensor volume of ~ 0.1 μm³. This work establishes the viability of spin defects in 2D materials for high frequency magnetometry, with wide-ranging applications across science and technology.

基于二维晶体中的自旋量子位的传感器提供了传感器和源之间纳米级接近的前景，这可以提供对其他方式无法访问的信号的访问。对于交流磁力测量，灵敏度和频率范围通常受到噪声频谱的限制，噪声频谱决定了量子位相干时间。我们使用相位调制连续级联动态去耦来解决这个问题，它将相干时间延长到室温下的T _{1极限，并实现可调谐窄带交流磁力测量。}利用六方氮化硼中带负电的硼空位的集合，我们检测到电子自旋共振范围在 ~ 10 − 150 MHz 范围内的面外交流场和 ± 150 MHz 范围内的面内场。我们测量约 2.5 GHz 时的交流磁场灵敏度为\(\sim 1\,\mu {{{\rm{T}}}}/\sqrt{{{{\rm{Hz}}}}}\)，传感器体积约为 0.1 μm ³。这项工作确立了二维材料中自旋缺陷用于高频磁力测量的可行性，在科学和技术领域具有广泛的应用。