A Solid-State Microwave Magnetometer with Picotesla-Level Sensitivity

TL;DR

This paper presents a high-sensitivity solid-state magnetometer operating at microwave frequencies near 2.87 GHz, achieving record sensitivity of 3.4 pT/√Hz using NV centers in diamond and noise cancellation techniques.

Contribution

It introduces a novel high-frequency quantum magnetometer with record sensitivity, combining custom NV diamond and noise cancellation for microwave sensing.

Findings

Achieved 3.4 pT/√Hz sensitivity at 2.87 GHz

Demonstrated amplitude and phase sensing capabilities

Projected tunability over 300 MHz range

Abstract

Quantum sensing of low-frequency magnetic fields using nitrogen-vacancy (NV) center ensembles has been demonstrated in multiple experiments with sensitivities as low as $\sim$1 pT/$\sqrt{\text{Hz}}$. To date, however, demonstrations of high-frequency magnetometry in the GHz regime with NV diamond are orders of magnitude less sensitive, above the nT/$\sqrt{\text{Hz}}$ level. Here we adapt for microwave frequencies techniques that have enabled high-performance, low-frequency quantum sensors. Using a custom-grown NV-enriched diamond combined with a noise cancellation scheme designed for high-frequency sensing, we demonstrate a Rabi-sequence-based magnetometer able to detect microwave fields near 2.87 GHz with a record sensitivity of 3.4 pT/$\sqrt{\textrm{Hz}}$. We demonstrate both amplitude and phase sensing and project tunability over a 300 MHz frequency range. This result increases the viability of NV ensembles to serve as microwave circuitry imagers and near-field probes of antennas.