# Direct Measurement of Quantum Efficiency of Single Photon Emitters in Hexagonal Boron Nitride

## TL;DR

This paper presents a direct, non-destructive method to measure the quantum efficiency of single photon emitters in hexagonal boron nitride, revealing very high efficiencies nearing 87%.

## Contribution

It introduces a novel approach using a metal hemisphere attached to an AFM tip for absolute QE measurement of SPEs in hBN.

## Key findings

- Emitters have quantum efficiencies up to 87%.
- The technique allows non-destructive, absolute QE measurement.
- High QEs are among the highest for solid-state SPEs.

## Abstract

Single photon emitters in two-dimensional materials are promising candidates for future generation of quantum photonic technologies. In this work, we experimentally determine the quantum efficiency (QE) of single photon emitters (SPE) in few-layer hexagonal boron nitride (hBN). We employ a metal hemisphere that is attached to the tip of an atomic force microscope to directly measure the lifetime variation of the SPEs as the tip approaches the hBN. This technique enables non-destructive, yet direct and absolute measurement of the QE of SPEs. We find that the emitters exhibit very high QEs approaching $(87 \pm 7)\,\%$ at wavelengths of $\approx\,580\,\mathrm{nm}$, which is amongst the highest QEs recorded for a solid state single photon emitter.