Generation of complex multi-photon states in miniaturized semiconductor based quantum devices

该项目的首要目标是通过半导体量子器件产生多光子态。这种多光子态在光子量子技术领域中具有最高的兴趣。例如，所谓的N光子NOON态允许超越经典极限的超精确相位测量。虽然具有优异量子性质的单光子可以通过高度优化的量子光源以发射率产生，但多光子态的产生仍处于起步阶段。由于多种应用场景和非常有趣的科学问题，人们对量子纳米光子学这一非常有吸引力和广泛未开发的领域的兴趣日益浓厚，相应的工作显示了相关方法的吸引力和可行性。然而，很明显，在量子技术中更先进的概念和应用方面的进一步进展需要对基本过程有更深入的了解，并更好地控制纳米光子学结构。在此背景下，本项目旨在通过将单个半导体量子点确定性地集成到微柱腔和微透镜中来控制多光子态的产生和研究。这种纳米光子集成增强了结构的光-物质相互作用和光子提取效率。量子点器件将与压电致动器相结合，通过改变施加的电压，以方便和可重复的方式控制它们的光谱特性。这些技术活动加上复杂的量子光谱学方法，如双光子共振激发，将成为拟议项目广泛实验研究的基础。科学问题集中在通过半导体量子点的双激子-激子级联产生多光子态。该级联的丰富物理特性及其通过双光子激发的跃迁共振驱动将用于通过级联修饰态之间的“蛙跳”过程产生例如双光子和N光子束。另一个关键活动将解决偏振纠缠光子对和N=4 NOON状态的创建，再次通过使用共振激发的双激子-激子级联。除此之外，我们计划通过使用双激子-激子光子对来执行弗兰森干涉术，以证明对贝尔不等式的违反。每项任务都将从三个伙伴之间的密集和密切互动中受益。计划中的合作是基于既有的和长期的共同经验。它使用并理想地补充了半导体技术和先进半导体光谱学相关团体的互补专业知识，以实现该项目的挑战性目标。

The overarching goal of the project is the generation of multi-photon states via semiconductor quantum devices. Such multi-photon states are of highest interest in the field of photonic quantum technology. For instance, so called N-photon NOON-states allow for ultra-precise phase measurements beyond classical limits. While single photons with excellent quantum nature can be generated with emission rates via highly optimized quantum-light sources, the creation of multi-photon states is still at its infancy. Because of the manifold application scenarios and very interesting scientific questions there has been strongly increasing interest in this very attractive and widely unexplored area of quantum nanophotonics, and corresponding works show the attractiveness and feasibility of related approaches. However, it has become clear that further progress in terms of more advanced concepts and applications in quantum technology require a much deeper understanding of the underlying processes and a better control of the nanophotonics sructures. Against this background the present project aims at the controlled generation and study of multiphoton-states by integration single semiconductor quantum dots deterministically into micropillar cavities and microlenses. This nanophotonics integration enhances both the light-matter interaction and the photon-extraction efficiency of the structures. The quantum dot devices will be combined with piezo-actuators to control their spectral properties in a convenient and reproducible way via variations of the applied voltage. These technological activities together with sophisticated quantum spectroscopy methods, such as two-photon resonant excitation, will be the basis for the extensive experimental studies of the proposed project. The scientific questions focus on the generation of multi-photon states via the biexciton-exciton cascade of semiconductor quantum dots. The rich physics of this cascade and the resonant drive of its transitions via two-photon excitation will be used to generate for instance two- and N-photon bundles by means of “leapfrog”-processes between dressed states of the cascade. A further key activity will address the creation of polarization entangled photon-pairs and N=4 NOON states, again by using the resonantly excited biexciton-exciton cascade. Beyond that we plan to perform Franson-interferometry by using biexciton-exciton photon-pairs to demonstrate the violation of Bell’s inequality. Each task will benefit in all aspects from an intensive and close interaction between the three partners. The planned cooperation is based on established and longstanding joint experience. It uses and ideally complements the complementary expertise of the involved groups in semiconductor technology and advanced semiconductor spectroscopy to reach the challenging goals of the project.