Resonant Excitation and Purcell Enhancement of Coherent Nitrogen-Vacancy Centers Coupled to a Fabry-P\'{e}rot Micro-Cavity

TL;DR

This paper demonstrates resonant excitation and Purcell enhancement of individual NV centers coupled to a fiber-cavity, significantly improving coherent photon emission rates and advancing quantum network scalability.

Contribution

It achieves resonant optical control of near-surface NV centers with Purcell enhancement, overcoming previous coherence limitations for quantum networking applications.

Findings

Purcell factors up to 4 were achieved.

Coherent photon detection probability can reach 10%.

Enhanced quantum emitter-cavity coupling at cryogenic temperatures.

Abstract

The nitrogen-vacancy (NV) center in diamond has been established as a prime building block for quantum networks. However, scaling beyond a few network nodes is currently limited by low spin-photon entanglement rates, resulting from the NV center's low probability of coherent photon emission and collection. Integration into a cavity can boost both values via the Purcell effect, but poor optical coherence of near-surface NV centers has so far prevented their resonant optical control, as would be required for entanglement generation. Here, we overcome this challenge, and demonstrate resonant addressing of individual, fiber-cavity-coupled NV centers, and collection of their Purcell-enhanced coherent photon emission. Utilizing off-resonant and resonant addressing protocols, we extract Purcell factors of up to 4, consistent with a detailed theoretical model. This model predicts that the probability of coherent photon detection per optical excitation can be increased to 10% for realistic parameters - an improvement over state-of-the art solid immersion lens collection systems by two orders of magnitude. The resonant operation of an improved optical interface for single coherent quantum emitters in a closed-cycle cryogenic system at T $\sim$ 4 K is an important result towards extensive quantum networks with long coherence.