Arash Ahmadi
V arious applications in quantum information require entangled photon sources that meet stringent criteria including brightness, near-unity fidelity, and low multi-photon emission. A quantum light source that meets all of these requirements at once is yet to be developed. In this work we present a source of entangled photon pairs, based on quantum dots in photonic nanowires, with a clear route to meet all of these criteria. Our results indicate that the source generates entangled photon pairs with no dephasing, during the emission lifetime. Therefore, measuring near-unity entanglement fidelity is limitted only by multi-photon emission of the source and the quality of the detection system, i.e. timing jitter and the dark counts. The latter has been largely disregarded in the literature and other features of the quantum dots, such as fine-structure splitting and spins interactions, have been reported to be the main obstacles in measuring perfect entanglement. Moreover, results attributed to resonant two-photon excitation and enhancement of the source in terms of pair-extraction efficiency and multi-photon emission will be presented. Based on our analysis, nanowire QDs have the potential to surpass the performance of spontaneous parametric down conversion sources. Furtheremore, we will also present a novel universal method to erase the fine-structure splitting of QDs using an all-optical approach.
Our results provide more insight into the nature of the two-photon biexciton-exciton cascade and demonstrate a clear path towards reaching perfect entanglement in semiconductor quantum dots in the future for the first time.
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