Quantum Acoustics with Semiconducting Artificial atoms

对于未来的量子技术，没有一种孤立的方法能满足实际设备的所有严格标准。在这里，混合量子系统介入并结合了不同单一系统的互补优势，同时避免了它们各自的缺点。我们项目的中心目标是利用固态物理学中最著名的三种激发：声、电荷和光，来证明这种混合量子平台的原理演示。在实践中，我们将开发表面声波（SAW）声子，单半导体量子点（QD）激子和光子之间的界面。将该平台从半经典状态带入全量子状态是迈向未来混合量子技术和应用的关键一步。为了达到这一目标，我们将我们的实验和理论专业知识结合起来，通过解决三个研究任务来实现一个综合工具箱，每个研究任务都集中在一个单独的构建块上，但所有研究任务都是相互关联的：(1)我们将发展理论和实验来研究散射光在单光子状态下不同声子边带通道之间的相干性。这一发展是基于我们现有的功能良好的共振荧光技术，它将扩展我们现有的关于声调制量子点和光子之间基本耦合机制的知识。这种新开发的干涉测量工具将用于所有其他任务。(2)我们将探索不同几何形状的声学谐振器中量子- saw -光的耦合。使用这种谐振器可以提高SAW的耦合效率，达到非结构化系统中无法达到的参数。我们将开发特定的谐振器设计，将数值模拟和尖端材料加工结合起来，以有意识地控制谐振器的声学特性。(3)最后一项任务是在量子态下声子-量子-光子相互作用的实验-理论联合研究。为了达到这个极限，声学谐振器必须冷却到它的量子基态，这将最终允许单声子控制，允许声子和光子域之间的互反量子转导。在这里，先前获得的对谐振器性能的洞察是至关重要的，并将有助于彻底探索经典到量子边界。随着新的理论方法和实验技术的发展，项目的每个阶段都会给研究领域带来创新。这不仅将推动我们考虑的基于声子、激子和光子的混合量子平台的方法，而且还将引发其他概念，例如利用磁振子形式的磁激励。

For future quantum technologies no isolated approach meets all the stringent criteria for practical devices. Here, hybrid quantum systems step in and combine complementary strengths of dissimilar single systems, while at the same time avoiding their individual shortcomings. The central objective of our project is the proof of principle demonstration of such a hybrid quantum platform utilizing the three best known excitations in solid state physics: Sound, charge and light. In practice we will develop an interface between surface acoustic wave (SAW) phonons, single semiconductor quantum dot (QD) excitons and photons. Bringing this platform from the semiclassical to the full quantum regime is a key step towards future hybrid quantum technologies and applications.To reach this goal we combine our experimental and theoretical expertise to realize a comprehensive toolbox by tackling three research task each focussing on an individual building block but all being interconnected: (1) We will develop theory and experiment for studying the coherence between different phonon sideband channels of the scattered light in the single-photon regime. The development is based on our existing well functioning resonance fluorescence technique and it will extend our existing knowledge about the fundamental coupling mechanism between the acoustically modulated QD and photons. This newly developed interferometry tool will be used in all other tasks. (2) We will explore the QD-SAW-light coupling in acoustic resonators of various geometries. The use of such resonators allows to increase the SAW’s coupling efficiency, reaching parameters that are not accessible in unstructured systems. We will develop specific resonator designs bringing together numerical simulations and cutting-edge material processing to deliberately control the acoustic properties of our resonators. (3) The final task is the joint experimental-theoretical study of the phonon-QD-photon interaction in the quantum regime. To reach this limit an acoustic resonator has to be cooled to its quantum ground states, which will ultimately allow single phonon control allowing reciprocal quantum transduction between the phononic and photonic domains. Here the previously gained insight into the resonator performance is of key importance and will help to thoroughly explore the classical to quantum boundary.Each stage of the project brings innovation to the research field, as new theoretical approaches and experimental techniques will be developed. These will not only push our considered approach for an hybrid quantum platform based on phonons, excitons and photons, but will also trigger other concepts that could for example utilize magnetic excitations in the form of magnons.