Diamond quantum magnetometer with dc sensitivity of < 10 pT Hz$^{-1/2}$ toward measurement of biomagnetic field

TL;DR

This paper reports a diamond quantum magnetometer achieving dc magnetic field sensitivity below 10 pT/Hz^{1/2}, suitable for biomagnetic measurements, with high stability and practical applicability.

Contribution

The work demonstrates a highly sensitive diamond quantum sensor with improved sensitivity and stability for biomagnetic field detection, advancing practical quantum sensing technologies.

Findings

Sensitivity of 9.4 pT/Hz^{1/2} in 5-100 Hz range

Detects sub-picotesla fields over thousands of seconds

Compatible with practical measurement setups

Abstract

We present a sensitive diamond quantum sensor with a magnetic field sensitivity of $9.4 \pm 0.1~\mathrm{pT/\sqrt{Hz}}$ in a near-dc frequency range of 5 to 100~Hz. This sensor is based on the continuous-wave optically detected magnetic resonance of an ensemble of nitrogen-vacancy centers along the [111] direction in a diamond (111) single crystal. The long $T_{2}^{\ast} \sim 2~\mathrm{\mu s}$ in our diamond and the reduced intensity noise in laser-induced fluorescence result in remarkable sensitivity among diamond quantum sensors. Based on an Allan deviation analysis, we demonstrate that a sub-picotesla field of 0.3~pT is detectable by interrogating the magnetic field for a few thousand seconds. The sensor head is compatible with various practical applications and allows a minimum measurement distance of about 1~mm from the sensing region. The proposed sensor facilitates the practical application of diamond quantum sensors.