Quantum and Many Body Physics Enabled by Advanced Semiconductor Nanotechnology

发光半导体材料和器件主导着日常生活的许多方面。他们的影响是无处不在的，提供了使互联网，大面积显示器，房间和街道照明的来源，仅举几个例子。它们的存在依赖于可以通过先进的晶体生长和复杂的纳米纤维制备的高质量半导体结构。我们的提案旨在利用先进的增长和制造技术，在量子世界中实现类似的进步，在量子世界中，往往违反直觉的行为只受量子力学定律的支配。我们的总体目标是探索纳米器件的行为，这些纳米器件在根本上新型的量子光子现象发生的制度中运行，有可能支撑下一代量子技术。我们专注于两个互补的系统：III-V族半导体具有高度完美的晶格，证明能够逐个发射光子和长相干量子态，以及原子薄的石墨烯状二维（2D）半导体，能够实现新的能带结构，稳定的电子-空穴束缚态（激子）和易于与图案化结构集成。这两种材料系统的结合是强大的，能够实现从单光子水平到相互作用占主导地位的密集多粒子状态的现象。我们的计划的一个重要部分集中在片上几何形状，使规模扩大可能需要的应用。我们所使用的半导体系统与光子有很强的相互作用;我们将实现通常不相互作用的光子之间的相互作用。我们将进入高度非线性腔量子电动力学的领域。激子（耦合的电子-空穴对）和光子强烈地相互作用，使得能级的阶梯能够导致在芯片上产生少数光子状态。通过将腔耦合在一起，我们的目标是光子的高度相关态。这些进展很可能是光子量子处理器和量子通信系统的重要组成部分。在类似的结构中，我们进入高密度的区域，其中电子和空穴凝聚成高度填充的状态（凝聚体）。我们的目标是回答长期存在的基本问题的类型的相变，可以发生在平衡系统和非平衡的损失平衡的增益。我们还将研究冷凝系统达到高温，可能超过100 K，以及相变到凝聚态的机制。凝聚态系统，除了他们的基本利益，也有潜力作为新形式的微型相干光源。纳米纤维将发挥至关重要的作用，使光的限制在亚波长的长度尺度和制造腔的光子，使他们有很长的寿命之前逃逸。在III-V纳米光子结构中放置高质量发射器的能力将从我们最近委托的晶体生长机中获得增强和潜在的世界领先地位，该晶体生长机专门为此目的而设计，由英国量子技术计划资助。类似的影响预计从我们的能力，以准备二维异质结构（原子薄层的两个单独的材料放置在另一个顶部）在无污染的超真空条件下，使实现的束缚电子空穴对状态的寿命非常长，途径冷凝到高密度状态。2D异质结构与图案化光子结构的简单集成进一步使非线性和量子现象得以研究，包括在光流不受缺陷散射影响的拓扑结构中。综上所述，我们具备了在基础量子光子学方面取得突破性进展的要素，并具有相当大的潜力来支撑下一代量子技术。

Light emitting semiconductor materials and devices dominate many aspects of everyday life. Their influence is all pervasive providing the sources which enable the internet, large area displays, room and street lighting to give just a few examples. Their existence relies on the high quality semiconductor structures which may be prepared by advanced crystal growth and sophisticated nanofabrication. Our proposal aims to capitalise on the advanced growth and fabrication to achieve similar advances in the quantum world where often counter-intuitive behaviour is governed solely by the laws of quantum mechanics. Our overall aim is to explore the behaviour of nano-devices operating in regimes where fundamentally new types of quantum-photonic phenomena occur, with potential to underpin the next generation of quantum technologies. We focus on two complementary systems: III-V semiconductors with their highly perfect crystal lattices, proven ability to emit photons one by one and long coherence quantum states, and atomically-thin graphene-like two dimensional (2D) semiconductors enabling new band structures, stable electron-hole bound states (excitons) and easy integration with patterned structures. The combination of the two material systems is powerful enabling phenomena ranging from the single photon level up to dense many-particle states where interactions dominate. A significant part of our programme focusses on on-chip geometries, enabling scale-up as likely required for applications. The semiconductor systems we employ interact strongly with photons; we will achieve interactions between photons which normally do not interact. We will gain entry into the regime of highly non-linear cavity quantum electrodynamics. Excitons (coupled electron-hole pairs) and photons interact strongly, enabling ladders of energy levels leading to on-chip production of few photon states. By coupling cavities together, we will aim for highly correlated states of photons. These advances are likely to be important components of photonic quantum processors and quantum communication systems. In similar structures, we access regimes of high density where electrons and holes condense into highly populated states (condensates). We aim to answer long-standing fundamental questions about the types of phase transitions that can occur in equilibrium systems and in out-of-equilibrium ones which have loss balanced by gain. We will also study condensate systems up to high temperatures, potentially in excess of 100K, and of the mechanisms underlying phase transitions to condensed states. The condensed state systems, besides their fundamental interest, also have potential as new forms of miniature coherent light sources.Nanofabrication will play a vital role enabling confinement of light on sub-wavelength length scales and fabrication of cavities for photons such that they have very long lifetimes before escaping. The ability to place high quality emitters within III-V nanophotonic structures will receive enhancement and potential world lead from a crystal growth machine we have recently commissioned, specially designed for this purpose, funded by the UK Quantum Technologies programme. Similar impact is expected from our ability to prepare 2D heterostructures (atomically thin layers of two separate materials placed one on top of the other) under conditions of ultrahigh vacuum free from contamination, enabling realisation of bound electron-hole pair states of very long lifetime, the route to condensation to high density states. The easy integration of 2D heterostructures with patterned photonic structures furthermore enables nonlinear and quantum phenomena to be studied, including in topological structures where light flow is immune to scattering by defects.Taken all together we have the ingredients in place to achieve ground-breaking advances in fundamental quantum photonics with considerable potential to underpin next generations of quantum technologies.