Nanodiamonds carrying quantum emitters with almost lifetime-limited linewidths

TL;DR

This paper reports the creation of nanodiamonds with quantum emitters that exhibit near lifetime-limited linewidths, achieved through a novel high-pressure high-temperature synthesis, advancing their potential in quantum technologies.

Contribution

The study demonstrates unprecedented narrow optical transitions of SiV centers in nanodiamonds produced by a new HPHT method, indicating high lattice quality and near lifetime-limited linewidths.

Findings

Spectral lines as narrow as 354 MHz in nanodiamonds smaller than 200 nm

Inhomogeneous distribution of 1.05 nm at 5 K across samples

Homogeneous linewidth corrected to about 200 MHz, close to lifetime limit

Abstract

Nanodiamonds (NDs) hosting optically active defects are an important technical material for applications in quantum sensing, biological imaging, and quantum optics. The negatively charged silicon vacancy (SiV) defect is known to fluoresce in molecular sized NDs (1 to 6 nm) and its spectral properties depend on the quality of the surrounding host lattice. This defect is therefore a good probe to investigate the material properties of small NDs. Here we report unprecedented narrow optical transitions for SiV colour centers hosted in nanodiamonds produced using a novel high-pressure high-temperature (HPHT) technique. The SiV zero-phonon lines were measured to have an inhomogeneous distribution of 1.05 nm at 5 K across a sample of numerous NDs. Individual spectral lines as narrow as 354 MHz were measured for SiV centres in nanodiamonds smaller than 200 nm, which is four times narrower than the best SiV line previously reported for nanodiamonds. Correcting for apparent spectral diffusion yielded a homogeneous linewith of about 200 MHz, which is close to the width limit imposed by the radiative lifetime. These results demonstrate that the direct HPHT synthesis technique is capable of producing nanodiamonds with high crystal lattice quality, which are therefore a valuable technical material.