Quantum and Many Body Physics Enabled by Advanced Semiconductor Nanotechnology

发光半导体材料和器件在日常生活的许多方面占主导地位。它们的影响无处不在，例如互联网、大面积显示器、房间和街道照明等。它们的存在依赖于高质量的半导体结构，这些结构可以通过先进的晶体生长和复杂的纳米加工来制备。我们的提议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，反直觉的行为通常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在新型量子光子现象发生的情况下的行为，这些现象有可能成为下一代量子技术的基础。我们专注于两个互补的系统：III-V半导体，它们具有高度完美的晶格，被证明具有一个接一个发射光子和长相干量子态的能力，以及原子级薄的石墨烯类二维（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）和易于与图像化结构集成。这两种材料系统的结合是强大的现象，从单光子水平到相互作用占主导地位的密集多粒子状态。我们的计划的一个重要部分集中在芯片上的几何形状，使规模可能需要的应用程序。我们使用的半导体系统与光子有强烈的相互作用；我们将实现光子之间的相互作用，而光子之间通常不会相互作用。我们将进入高度非线性腔量子电动力学的领域。激子（耦合电子-空穴对）和光子相互作用强烈，使能级阶梯导致芯片上产生少数光子态。通过将空腔耦合在一起，我们的目标是光子的高度相关状态。这些进展很可能成为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，我们接触到高密度的状态，在那里电子和空穴凝聚成高密度的状态（凝聚物）。我们的目标是回答长期存在的关于相变类型的基本问题，这些相变可能发生在平衡系统和非平衡系统中，这些系统的损失与增益相平衡。我们还将研究高达高温的冷凝系统，可能超过100K，以及相变到凝聚态的机制。凝聚态系统，除了他们的基本兴趣，也有潜力作为微型相干光源的新形式。纳米制造将在亚波长尺度上限制光和制造光子腔方面发挥至关重要的作用，从而使光子在逃逸之前具有很长的寿命。在III-V纳米光子结构中放置高质量发射器的能力将得到增强，并可能从我们最近委托的晶体生长机器中获得世界领先地位，该机器是由英国量子技术计划资助的，专门为此目的而设计的。我们在无污染的超高真空条件下制备二维异质结构（两种独立材料的原子薄层叠加在一起）的能力预计也会产生类似的影响，从而实现寿命非常长的束缚电子-空穴对状态，这是凝结到高密度状态的途径。二维异质结构与图像化光子结构的容易集成进一步使非线性和量子现象得以研究，包括光流不受缺陷散射的拓扑结构。综上所述，我们已经具备了在基础量子光子学方面取得突破性进展的要素，并具有支撑下一代量子技术的巨大潜力。

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.