Semiconductor Nanowire-based Quantum Light Sources for Quantum Networks

量子网络，无论是作为安全传输信息的平台，还是在孤立的少量子位量子计算机之间共享量子信息的平台，正在成为现实。要建立这样的网络，需要量子光源工作在光纤损耗最小的波长（1310和1550nm）。为了达到足够的传输速率，量子光源需要产生接近统一效率的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），其效率限制在~1%。****本研究计划提出开发片上量子光源，将III-V纳米线量子点（NW QDs）的优异光学特性与硅基光子学的低传播损耗结合起来。长期目标是提供一种可扩展的解决方案，以接近统一的效率和高重复率产生量子光。重要的是，这些光子将以与长途电信光纤兼容的电信波长产生。这些源的可用性将极大地促进它们在安全量子网络中的实现，其中原理证明已经得到证明，并且可以预见更高密钥传输速率的驱动。****我们有一个既定的过程，即在生长基质上预先选择的位置生长单个NW量子点。重要的是，NW几何结构适合于芯片上集成的“选择和放置”方法，本质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上拾取单个NWs并将它们放置在用适当的光子电路制备的衬底上的特定位置来实现。****该研究计划将从使用SiN片上平台（PhD #1）优化在~900nm波长下工作的设备的源效率开始。光子结构（波导、谐振器）将设计为最佳耦合和自发发射率。*该项目的下一阶段将开发电信波长为1310nm和1550nm的NW源（PhD#2）。这些源将使用绝缘体上硅（SOI）平台集成在芯片上。在SiN光子电路中获得的专有技术将应用于Si，以生产以GHz发射速率工作的电信波长源（PhD #1&2）。*同时，对NW量子点的量子光学特性及其与环境的相互作用的理论理解将得到发展（PDF#1）。******该项目的最后阶段将探索几何形状和生长条件，III-V型NWs可以直接在Si上生长，生长方向与衬底平行（博士论文#3）。如果成功，这种生长模式可以应用于预制SOI光子电路，在预先选择的位置生长电信波长单量子点，这是一个真正可扩展的片上平台

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.***