Single germanium vacancy centres in nanodiamonds with bulk-like spectral stability

TL;DR

This study demonstrates that single germanium-vacancy centres in nanodiamonds exhibit stable spectral properties and high polarization, making them promising for quantum technologies like secure communication.

Contribution

It provides the first detailed characterization of GeV$^-$ centres in nanodiamonds, highlighting their spectral stability and suitability for quantum applications.

Findings

Maximum photon emission rate of 1.6 MHz at saturation

Polarization visibility of 92% in fluorescence light

Spectral stability comparable to bulk GeV$^-$ centres

Abstract

Motivated by the success of group IV colour centres in nanodiamonds (NDs) for hybrid technology requiring a single photon source, we study single germanium-vacancy (GeV$^-$) centres in NDs at room temperature with size rangingfrom 10 to 50 nm and with remarkable spectral properties. We characterize their zero-phonon line (ZPL), study their internal population dynamics and compare their emission properties in the framework of a three level model with intensity dependent de-shelving. Furthermore, we characterize their lifetime, polarization and brightness. We find amaximum photon emission count rate of 1.6 MHz at saturation. We also report a polarization visibility of 92% from the fluorescence light, which potentially makes GeV$^-$ centres good candidates for quantum key distribution (QKD)requiring polarized single photons. We show that the GeV$^-$ in NDs presented in this work have a comparable spectral stability compared to their bulk counterpart which is needed for future applications using NDs.