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. In a collaboration with theorists from Huazhong University of Science and Technology (China), The Hebrew University of Jerusalem (Israel) and University of Ulm, we adapted a dynamical decoupling scheme that improves phase coherence by orders of magnitude and merged it with a magnetic sensing protocol.
This allowed us to achieve a measurement sensitivity close to the standard quantum limit, even for high frequency fields. Using a single atomic ion as a sensor, we experimentally attain a sensitivity of 4.6 pT/√Hz for an alternating-current magnetic field near 14 MHz. 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.