# Multiphoton resonances in nitrogen-vacancy defects in diamond

## TL;DR

This paper investigates the enhancement of multiphoton responses in nitrogen-vacancy (NV) centers in diamond through coupling with superconducting cavities or P1 defect ensembles, improving magnetic field sensitivity and enabling hyperfine splitting probing.

## Contribution

It demonstrates how coupling NV centers to cavities or P1 ensembles enhances their nonlinear response and sensitivity, with practical applications in magnetometry.

## Key findings

- Enhanced multiphoton response via cavity coupling.
- Probing of P1 hyperfine splitting using NV ensembles.
- Increased magnetic field responsivity in coupled systems.

## Abstract

Dense ensembles of nitrogen vacancy (NV) centers in diamond are of interest for various applications including magnetometry, masers, hyperpolarization and quantum memory. All of the applications above may benefit from a non-linear response of the ensemble, and hence multiphoton processes are of importance. We study an enhancement of the NV ensemble multiphoton response due to coupling to a superconducting cavity or to an ensemble of Nitrogen 14 substitutional defects (P1). In the latter case, the increased NV sensitivity allowed us to probe the P1 hyperfine splitting. As an example of an application, an increased responsivity to magnetic field is demonstrated.