# All-optical nuclear quantum sensing using nitrogen-vacancy centers in diamond

## TL;DR

Researchers developed a new all-optical method for quantum sensing using nitrogen-vacancy centers in diamond, eliminating the need for microwave or radio-frequency signals.

## Contribution

The paper introduces a purely optical approach to quantum sensing using NV centers, enabling compact and efficient sensors.

## Key findings

- An all-optical method was demonstrated for optically pumping the 15N nuclear spin into a quantum superposition state.
- Free-induction decay measurements were achieved on both single spins and spin ensembles using the new approach.
- The technique enables low-frequency quantum sensing without microwave or radio-frequency driving.

## Abstract

Solid state spins have demonstrated significant potential in quantum sensing with applications including fundamental science, medical diagnostics and navigation. The quantum sensing schemes showing best performance under ambient conditions all utilize microwave or radio-frequency driving, which poses a significant limitation for miniaturization, energy efficiency, and non-invasiveness of quantum sensors. We overcome this limitation by demonstrating a purely optical approach to coherent quantum sensing. Our scheme involves the 15N nuclear spin of the Nitrogen-Vacancy (NV) center in diamond as a sensing resource, and exploits NV spin dynamics in oblique magnetic fields near the NV’s excited state level anti-crossing to optically pump the nuclear spin into a quantum superposition state. We demonstrate all-optical free-induction decay measurements—the key protocol for low-frequency quantum sensing—both on single spins and spin ensembles. Our results pave the way for highly compact quantum sensors to be employed for magnetometry or gyroscopy applications in challenging environments.