Ultrasensitive Magnetometer Using a Single Atom

TL;DR

This paper demonstrates an ultrasensitive magnetometer using a single atomic ion, achieving near quantum-limited sensitivity at high frequencies, with potential applications in nanoscale magnetic imaging.

Contribution

The authors develop a magnetometry protocol combining dynamical decoupling with a single atom sensor, reaching unprecedented sensitivity levels.

Findings

Achieved 4.6 pT/√Hz sensitivity at 14 MHz.

Extended coherence time T2 by orders of magnitude.

Demonstrated potential for high-resolution magnetic imaging.

Abstract

Precision sensing, and in particular high precision magnetometry, is a central goal of research into quantum technologies. For magnetometers, often trade-offs exist between sensitivity, spatial resolution, and frequency range. The precision, and thus the sensitivity of magnetometry, scales as $1/\sqrt {T_2}$ with the phase coherence time, $T_2$, of the sensing system playing the role of a key determinant. Adapting a dynamical decoupling scheme that allows for extending $T_2$ by orders of magnitude and merging it with a magnetic sensing protocol, we achieve a measurement sensitivity even for high frequency fields close to the standard quantum limit. Using a single atomic ion as a sensor, we experimentally attain a sensitivity of $4.6$ pT $/\sqrt{Hz}$ for an alternating-current magnetic field near 14 MHz. Based on the principle demonstrated here, this unprecedented sensitivity combined with spatial resolution in the nanometer range and tunability from direct-current to the gigahertz range could be used for magnetic imaging in as of yet inaccessible parameter regimes.