# Deterministic enhancement of coherent photon generation from a nitrogen-vacancy center in ultrapure diamond

## TL;DR

This paper demonstrates a microcavity approach that significantly enhances coherent photon emission from NV centers in diamond, improving efficiency and enabling better quantum information applications.

## Contribution

It introduces a minimally processed diamond microcavity platform that boosts photon emission rates and coherence from NV centers, overcoming fabrication challenges.

## Key findings

- Purcell factor of 2.0 observed in experiments
- Zero phonon line emission probability increased from 3% to 46%
- Lifetime tuning confirms cavity-induced emission enhancement

## Abstract

The nitrogen-vacancy (NV) center in diamond has an optically addressable, highly coherent spin. However, an NV center even in high quality single-crystalline material is a very poor source of single photons: extraction out of the high-index diamond is inefficient, the emission of coherent photons represents just a few per cent of the total emission, and the decay time is large. In principle, all three problems can be addressed with a resonant microcavity. In practice, it has proved difficult to implement this concept: photonic engineering hinges on nano-fabrication yet it is notoriously difficult to process diamond without degrading the NV centers. We present here a microcavity scheme which uses minimally processed diamond, thereby preserving the high quality of the starting material, and a tunable microcavity platform. We demonstrate a clear change in the lifetime for multiple individual NV centers on tuning both the cavity frequency and anti-node position, a Purcell effect. The overall Purcell factor $F_{\rm P}=2.0$ translates to a Purcell factor for the zero phonon line (ZPL) of $F_{\rm P}^{\rm ZPL}\sim30$ and an increase in the ZPL emission probability from $\sim 3 \%$ to $\sim 46 \%$. By making a step-change in the NV's optical properties in a deterministic way, these results pave the way for much enhanced spin-photon and spin-spin entanglement rates.