Solid-state ensemble of highly entangled photon sources at rubidium atomic transitions

TL;DR

This paper demonstrates a wafer-scale ensemble of GaAs/AlGaAs quantum dots that reliably emit highly entangled photon pairs at rubidium atomic transitions, advancing solid-state quantum communication technologies.

Contribution

It introduces a new growth method for quantum dots achieving near 100% entangled photon emitters without post-growth tuning, with record high entanglement fidelity and narrow wavelength distribution.

Findings

Near 100% of quantum dots emit entangled photons

Record high entanglement fidelity of 0.91

Ultra-narrow wavelength distribution at rubidium transitions

Abstract

Semiconductor InAs/GaAs quantum dots grown by the Stranski-Krastanov method are among the leading candidates for the deterministic generation of polarization entangled photon pairs. Despite remarkable progress in the last twenty years, many challenges still remain for this material, such as the extremely low yield (<1% quantum dots can emit entangled photons), the low degree of entanglement, and the large wavelength distribution. Here we show that, with an emerging family of GaAs/AlGaAs quantum dots grown by droplet etching and nanohole infilling, it is possible to obtain a large ensemble (close to 100%) of polarization-entangled photon emitters on a wafer without any post-growth tuning. Under pulsed resonant two-photon excitation, all measured quantum dots emit single pairs of entangled photons with ultra-high purity, high degree of entanglement (fidelity up to F=0.91, with a record high concurrence C=0.90), and ultra-narrow wavelength distribution at rubidium transitions. Therefore, a solid-state quantum repeater - among many other key enabling quantum photonic elements - can be practically implemented with this new material.