Efficient Sources of Entangled Photon Pairs Based on Deterministic Quantum Dot Microlenses

在本计画中，我们将结合In（Ga）As量子点在（111）面GaAs衬底上的生长、单片集成微透镜的原位阴极发光光刻（CLL）和共振激发方案的优点，开发出偏振纠缠光子对的确定性和超亮光源。这些量子光源是先进量子通信方案（例如基于纠缠分布的量子中继器）的关键元件。在我们的概念中，单个（111）量子点在有源区的源将能够通过双激子（XX）-激子（X）辐射级联产生偏振纠缠光子对，因为它们的特定的电子结构，这些量子点的精细结构分裂减少。使用CLL，这样的QD将被确定性地集成到微透镜中，与较低的反射镜部分相结合，确保XX和X发射的宽带增强，预测的提取效率超过80%。这些量子光源的全部潜力将通过共振激发方案来探索，该方案旨在按需发射具有记录亮度和不可分辨性的偏振纠缠光子对。为此，我们的概念在量子通信领域的高潜力将通过在共振双光子π脉冲激发下进行分离源发射的双光子干涉实验来证明。

In this project, we will develop deterministic and ultra-bright sources of polarization entangled photon pairs by combining the advantages of In(Ga)As QD grown on (111) oriented GaAs substrate, in-situ cathodoluminescence lithography (CLL) of monolithically integrated microlenses, and resonant excitation schemes. These quantum light sources are key elements of advanced quantum communication schemes, such as the quantum repeater, which are based on entanglement distribution. In our concept, single (111) QDs in the active region of the sources will enable the generation of polarization-entangled photon-pairs via the biexciton (XX) - exciton (X) radiative cascade because of their specific electronic structure of these QDs with diminishing fine-structure splitting. Using CLL, such QDs will be deterministically integrated into microlenses which, in combination with lower mirror section, ensure broadband enhancement of XX and X emission with a predicted extraction efficiency beyond 80 %. The full potential of these quantum light sources will be explored by resonant excitation schemes aiming at the on-demand emission of polarization entangled photon pairs with record brightness and indistinguishability. To this end, the high potential of our concept in the field of quantum communication will be demonstrated by performing two-photon interference experiments of emission from separated sources under resonant two-photon pi-pulse excitation.