Phys.org March 25, 2024
An on-demand source of bright entangled photon pairs is needed for quantum key distribution (QKD) and quantum repeaters. The generation of such pairs is based on spontaneous parametric down-conversion (SPDC) in non-linear crystals. However, SPDC pair extraction efficiency is very limited when operating at near-unity fidelity. In principle quantum dots in photonic nanostructures can overcome this limit, but the devices with high entanglement fidelity have low pair extraction efficiency. An international team of researchers (Canada, the Netherlands, Sweden) has demonstrated a measured peak entanglement fidelity of 97.5% ± 0.8% and pair extraction efficiency of 0.65% from an InAsP quantum dot in an InP photonic nanowire waveguide. The oscillating two-photon Bell state they generated could establish a secure key for peer-to-peer QKD. According to the researchers their time-resolved QKD scheme does not require the removal of the quantum dot energy splitting of the intermediate exciton states in the biexciton-exciton cascade… read more. Open Access TECHNICAL ARTICLE
Resonant excitation of the nanowire quantum dot. Credit: Communications Physics volume 7, Article number: 62 (2024)