Phonon dephasing and spectral diffusion of quantum emitters in hexagonal Boron Nitride

TL;DR

This study investigates the factors limiting the spectral purity of quantum emitters in hexagonal boron nitride, focusing on phonon dephasing and spectral diffusion at cryogenic temperatures, to improve their application in quantum optics.

Contribution

It provides detailed measurements of phonon dephasing and spectral diffusion in hBN quantum emitters, highlighting how these effects influence linewidths and can be minimized for quantum interference.

Findings

Linewidths are phonon broadened, around 1 GHz at 5K.

Spectral diffusion dominates at higher pump powers.

Working below saturation reduces spectral diffusion.

Abstract

Quantum emitters in hexagonal boron nitride (hBN) are emerging as bright and robust sources of single photons for applications in quantum optics. In this work we present detailed studies on the limiting factors to achieve Fourier Transform limited spectral lines. Specifically, we study phonon dephasing and spectral diffusion of quantum emitters in hBN via resonant excitation spectroscopy at cryogenic temperatures. We show that the linewidths of hBN quantum emitters are phonon broadened, even at 5K, with typical values of the order of one GHz. While spectral diffusion dominates at increasing pump powers, it can be minimized by working well below saturation excitation power. Our results are important for future utilization of quantum emitters in hBN for quantum interference experiments.