Strain-Tunable GaAs Quantum dot: A Nearly Dephasing-Free Source of Entangled Photon Pairs on Demand

TL;DR

This paper presents a strain-tunable GaAs quantum dot source that produces nearly maximally entangled photon pairs on demand with high fidelity and concurrence, avoiding complex post-selection techniques, and suitable for quantum communication.

Contribution

The study demonstrates a nearly dephasing-free, on-demand entangled photon source using strain-tunable GaAs quantum dots driven by two-photon excitation, achieving high entanglement fidelity without post-selection.

Findings

Achieved polarization-entangled photons with fidelity 0.978 and concurrence 0.97.

Overcame decoherence with modest Purcell enhancement to surpass 0.99 entanglement.

Showed GaAs quantum dots are suitable for advanced quantum communication protocols.

Abstract

Entangled photon generation from semiconductor quantum dots via the biexciton-exciton cascade underlies various decoherence mechanisms related to the solid-state nature of the quantum emitters. So far, this has prevented the demonstration of nearly-maximally entangled photons without the aid of inefficient and complex post-selection techniques that are hardly suitable for quantum communication technologies. Here, we tackle this challenge using strain-tunable GaAs quantum dots driven under two-photon resonant excitation and with strictly-degenerate exciton states. We demonstrate experimentally that our on-demand source generates polarization-entangled photons with fidelity of 0.978(5) and concurrence of 0.97(1) without resorting to post-selection techniques. Moreover, we show that the remaining decoherence mechanisms can be overcome using a modest Purcell enhancement so as to achieve a degree of entanglement >0.99. Our results highlight that GaAs quantum dots can be readily used in advanced communication protocols relying on the non-local properties of quantum entanglement.