# Multipoint Lock-in Detection for Diamond Nitrogen-Vacancy Magnetometry Using DDS-Based Frequency-Shift Keying

## TL;DR

This paper introduces a new method for detecting multiple resonant points in diamond nitrogen-vacancy sensors using a single device, enabling efficient and portable quantum sensing.

## Contribution

A novel multipoint lock-in detection scheme using DDS-based FSK for NV magnetometry is proposed.

## Key findings

- The method allows frequency hopping up to 1.4 GHz bandwidth.
- It can encode an unlimited number of resonant points during sensing.
- The technique is experimentally validated for quantum multi-frequency excitation.

## Abstract

In recent years, the nitrogen-vacancy (NV) center in diamonds has been demonstrated to be a high-performance multiphysics sensor, where a lock-in amplifier (LIA) is often adopted to monitor photoluminescence changes around the resonance. It is rather complex when multiple resonant points are utilized to realize a vector or temperature-magnetic joint sensing. In this article, we present a novel scheme to realize multipoint lock-in detection with only a single-channel device. This method is based on a direct digital synthesizer (DDS) and frequency-shift keying (FSK) technique, which is capable of freely hopping frequencies with a maximum of 1.4 GHz bandwidth and encoding an unlimited number of resonant points during the sensing process. We demonstrate this method in experiments and show it would be generally useful in quantum multi-frequency excitation applications, especially in the portable and highly mobile cases.