Quantum Photonic Integrated Circuits Operating at Cryogenic Temperatures

光子集成电路（PIC）在过去十年中发展迅速，使光学系统集成到单个芯片上。此外，电子和光子学在芯片上的集成支撑了电信，传感和最近的量子信息处理的进步。在量子系统中，光子可以用作固态量子节点之间的通信层或量子比特本身。PIC的紧凑尺寸和机械稳定性使其成为大规模光信号路由和处理的一个有吸引力的选择。一个主要的挑战在于这些PIC的可重构性。为了允许灵活和可控的电路，用于调谐光学组件的机制是必要的。电信应用领域的现有技术使用PIN结二极管或热加热器元件来在波导材料中产生吸收或折射率变化。对于量子系统来说，这两种方法都不是理想的，前者将噪声光子引入电路，后者将热源引入许多单光子源和探测器技术所需的低温条件。在本项目中，将开发一种新的方法来调谐PIC，该方法与低温和低功耗操作兼容。为了实现这一目标，将使用混合集成方法将不同的光学材料集成在单个芯片上。二阶非线性响应材料将用于通过直接电子控制来产生折射率变化，与低温环境中的操作兼容。学生将对器件进行数值模拟，以优化几何形状和电路布局，然后用于PIC系统的制造。学生将负责在最先进的光学实验室中测量所产生的PIC系统，并使用经典和单光子敏感测量设备。测量结果将用于反馈到优化的制造过程中，最终的电路设计将用于实现量子信息处理实验。学生将成为一个更大的研究小组的一部分，有机会在一个充满热情的大学团队中与他人合作。研究结果将发表在高影响力的期刊上，并有机会在国际会议上发表。

Photonic Integrated Circuits (PICs) have developed rapidly over the last decade, enabling the miniaturisation of optical systems onto a single chip. Furthermore, the integration of electronics and photonics on a chip have underpinned advances in telecommunications, sensing, and recently, quantum information processing. In quantum systems photons can be used as a communications layer between solid-state quantum nodes or as qubits themselves. The compact size and mechanical stability of PICs make them an attractive option for the routing and processing of optical signals at significant scale.One major challenge lies in the reconfigurability of these PICs. To allow for flexible and controllable circuits, a mechanism for tuning optical components is necessary. The current state of the art in the field for telecommunications applications uses PIN junction diodes or thermal heater elements to create absorption or refractive index changes in the waveguiding material. For quantum systems neither of these methods are ideal, with the former introducing noise photons to the circuit and the latter introducing thermal sources into the cryogenic conditions necessary for many of the single photon source and detector technologies employed.In this project a new method for tuning PICs will be developed that is compatible with cryogenic and low power consumption operation. To achieve this a hybrid integration method will be used to integrate different optical materials together on a single chip. Second order non-linear response materials will be used to create refractive index changes by direct electronic control, compatible with operation in cryogenic environments.The student will carry out numerical simulations of devices to optimise the geometries and circuit layouts which will then be used for fabrication of PIC systems. The student will be responsible for the measurement of the resultant PIC systems in state-of-the-art optical laboratories with access to classical and single photon sensitive measurement equipment. Measurement results will be used to feedback into optimisation of the fabrication process with final circuit designs being used to implement quantum information processing experiments. The student will be part of a larger research group with the opportunity to work with others in a collegiate and enthusiastic team. Research findings will be published in high impact journals with the opportunity to present at an international conference.