Revealing Collective Emission in the Single-to-Bulk Transition of Quantum Emitters in Nanodiamond Agglomerates

TL;DR

This study investigates the transition from individual to collective emission in nanodiamond agglomerates, revealing a length scale of about three wavelengths and proposing a new fluctuation-based measure to detect collective effects.

Contribution

It introduces a novel fluctuation-based method to detect collective emission effects in nanodiamond ensembles, addressing limitations of traditional correlation functions.

Findings

Transition to bulk emission occurs at ~3 wavelengths from the emitter

Second-order correlation function fails to detect collective effects in this system

Proposes a new fluctuation-based measure to identify collective emission

Abstract

Individual quantum emitters form a fundamental building block for emerging quantum technologies. Collective effects of such emitters might improve the performance of applications even further. When scaling materials to larger sizes, however, collective effects might be covered by transitions to bulk properties. Here, we probe the optical properties of Nitrogen Vacancy (NV) centers in agglomerates of nanodiamonds. We quantify the transition from individual emitters to bulk emission by fluorescence lifetime measurements, and find a transition to occur on a length scale of $\sim 3$ wavelengths around the emitter. While our lifetime measurements are consistent with superradiant decay, the second-order correlation function, which is a standard measure to reveal collective properties, fails to probe collective effects for our case of an ensemble of collectively contributing domains to the emission. Therefore, we propose and apply a new measure to trace collective effects based on the fluctuation statistics of the emitted light. Our work points toward systematically studying collective effects in a scalable solid-state quantum system, and using them for quantum optical applications in agglomerates of highly-doped nanodiamonds.