High-resolution, Wide-frequency-range Magnetic Spectroscopy with Solid-state Spin Ensembles

TL;DR

This paper introduces a novel magnetic spectroscopy method using solid-state spin ensembles that achieves high spectral resolution over a broad frequency range, enabling advanced applications in RF, MW, and NMR spectroscopy.

Contribution

The work presents a new protocol combining quantum frequency mixing with synchronized readout to extend NV-diamond magnetic spectroscopy to higher frequencies with sub-Hz resolution.

Findings

Achieved detection of signals from 10 MHz to 4 GHz.

Demonstrated sub-Hz spectral resolution with nT sensitivity.

Enabled phase measurement accuracy better than 1 degree.

Abstract

Quantum systems composed of solid-state electronic spins can be sensitive detectors of narrowband magnetic fields. A prominent example is the nitrogen-vacancy (NV) center in diamond, which has been employed for magnetic spectroscopy with high spatial and spectral resolution. However, NV-diamond spectroscopy protocols are typically based on dynamical decoupling sequences, which are limited to low-frequency signals ($\lesssim{20}\,$MHz) due to the technical requirements on microwave (MW) pulses used to manipulate NV electronic spins. In this work, we experimentally demonstrate a high-resolution magnetic spectroscopy protocol that integrates a quantum frequency mixing (QFM) effect in a dense NV ensemble with coherently averaged synchronized readout (CASR) to provide both a wide range of signal frequency detection and sub-Hz spectral resolution. We assess the sensitivity of this QFM-CASR protocol across a frequency range of 10$\,$MHz to 4$\,$GHz. By measuring the spectra of multi-frequency signals near 0.6, 2.4 and 4$\,$GHz, we demonstrate sub-Hz spectral resolution with a nT-scale noise floor for the target signal, and precise phase measurement with error $<1^\circ$. Compared to state-of-the-art NV-diamond techniques for narrowband magnetic spectroscopy, the QFM-CASR protocol greatly extends the detectable frequency range, enabling applications in high-frequency radio frequency (RF) and MW signal microscopy and analysis, as well as tesla-scale nuclear magnetic resonance (NMR) spectroscopy of small samples.