Generation of maximally entangled states and coherent control in quantum dot microlenses

TL;DR

This paper demonstrates that quantum dot microlenses can efficiently generate high-fidelity entangled photon pairs and achieve coherent control, advancing nanophotonic quantum information technologies.

Contribution

It shows that entanglement fidelity close to unity is achievable in quantum dot microlenses despite fine-structure splitting, and demonstrates coherent control of biexcitonic states.

Findings

High-fidelity entanglement achieved despite FSS

Entanglement preserved over the excitonic wave-packet

Coherent control of biexcitonic state demonstrated

Abstract

The integration of entangled photon emitters in nanophotonic structures designed for the broadband enhancement of photon extraction is a major challenge for quantum information technologies. We study the potential of quantum dot (QD) microlenses to act as efficient emitters of maximally entangled photons. For this purpose, we perform quantum tomography measurements on InGaAs QDs integrated deterministically into microlenses. Even though the studied QDs show non-zero excitonic fine-structure splitting (FSS), polarization entanglement can be prepared with a fidelity close to unity. The quality of the measured entanglement is only dependent on the temporal resolution of the used single-photon detectors compared to the period of the excitonic phase precession imposed by the FSS. Interestingly, entanglement is kept along the full excitonic wave-packet and is not affected by decoherence. Furthermore, coherent control of the upper biexcitonic state is demonstrated.