Semiconductor Nanowire-based Quantum Light Sources for Quantum Networks

无论是作为安全传输信息的平台，还是在孤立的几个量子比特的量子计算机之间共享量子信息的平台，量子网络都正在成为现实。要建立这样的网络，将需要工作在光纤损耗最小的波长(1310和1550 nm)的量子光源。为了获得足够的传输速率，量子光源将需要以接近统一的效率产生单光子和纠缠光子对。目前，光源是概率的(非线性晶体或衰减激光器)，将效率限制在~1%。*本研究计划建议开发结合III-V纳米线量子点(NW量子点)的优异光学特性和硅基光子学的低传播损耗的片上量子光源。长期目标是提供一种可扩展的解决方案，以产生接近单位效率的量子光，并在高重复频率下可用。重要的是，这些光子将在与长途电信光纤兼容的电信波长上产生。这种源的可获得性将极大地促进它们在安全量子网络中的实施，在安全量子网络中，已经证明了原理，并且可以预见到对更高密钥传输率的驱动。*我们有一个既定的过程，即在生长衬底上的预选位置生长单个NW量子点。重要的是，NW几何结构为芯片集成提供了一种“拾取和放置”的方法，基本上允许对单个量子发射器进行物理操作。片上集成将通过从生长衬底中拾取单个NW，并将它们放置在采用适当光子电路准备的衬底上的特定位置来实现。*研究计划将从使用SIN片上平台(PHD#1)优化在~900 nm波长运行的设备的源效率开始。将为最佳耦合和自发发射率设计光子结构(波列、谐振器)。*该项目的下一阶段将开发电信波长为1310 nm和1550 nm的NW源(PHD#2)。这些电源将使用绝缘体上硅(SOI)平台集成到芯片上。在SIN光子电路中获得的技术将应用于硅，以生产以GHz发射率工作的电信波长源(PHD#1和PHD#2)。*同时，将从理论上理解NW量子点的量子光学性质及其与环境的相互作用(PDF#1)。*项目的最后阶段将探索几何结构和生长条件，从而可以以平行于衬底的生长方向在Si上直接生长III-V NW(PHD#3)。如果成功，这种生长模式可以应用于预制的SOI光子电路，在预选位置生长电信波长单量子点，真正实现可扩展的片上平台。*

The quantum network, whether as a platform to transfer information securely or to share quantum information amongst isolated few-qubit quantum computers, is becoming a reality. To build such a network will require quantum light sources operating at wavelengths where fibre losses are minimum (1310 and 1550nm). In order to achieve sufficient transmission rates, the quantum light sources will need to produce single photons and entangled photon pairs with near-unity efficiency. At present, sources are probabilistic (non-linear crystals or attenuated lasers) which limit efficiencies to ~1%.****This program of research proposes to develop on-chip quantum light sources that combine the excellent optical properties of III-V nanowire quantum dots (NW QDs) with the low propagation losses of silicon-based photonics. The long term goal is to provide a scalable solution to generating quantum light with near unity efficiency and available at high repetition rates. Importantly, these photons will be generated at telecom wavelengths compatible with long-haul telecommunication fibres. The availability of such sources will greatly facilitate their implementation in secure quantum networks, where proof of principle has already been demonstrated and a drive for higher key transfer rates is foreseeable.****We have an established process whereby individual NW QDs are grown at pre-selected positions on the growth substrate. Importantly, the NW geometry lends itself to a “pick and place” approach for on-chip integration, essentially allowing for the physical manipulation of single quantum emitters. On-chip integration will be achieved by picking up individual NWs from the growth substrate and placing them at specific locations on a substrate prepared with the appropriate photonic circuitry.****The research program will start with optimizing source efficiency for devices operating at wavelengths of ~900nm using a SiN on-chip platform (PhD #1). Photonic structures (wavequides, resonators) will be designed for optimal coupling and spontaneous emission rates.*The next stage of the project will develope NW sources at telecom wavelengths of 1310nm and 1550nm (PhD#2). These sources will be integrated on-chip using a silicon-on-insulator (SOI) platform. The know-how gained in SiN photonic circuits will be applied to Si to produce telecom wavelength sources operating at GHz emission rates (PhD #1&2).*In parallel, a theoretical understanding of the quantum optical properties of NW QDs and their interactions with the environment will be developed (PDF#1).******The last stage of the project will explore geometries and growth conditions whereby the III-V NWs can be grown directly on Si with a growth direction parallel to the substrate (PhD #3). If successful, this growth mode can be applied to pre-fabricated SOI photonic circuits to grow telecom wavelength single QDs at pre-selected positions, a truly scalable on-chip platform.***