Long-Range Exchange Coupling between Ge-Hole Spin Quantum Systems

量子处理器承诺解决经典计算机认为无法解决的问题，推动金融、气候变化、化学和密码学等领域的发展。目前量子计算的领先平台包括超导量子比特、离子陷阱和量子点中的自旋。虽然在这样的平台上已经有了许多关于单量子比特操作的实验，但两个量子比特的纠缠操作仍然难以捉摸，这是实现有用的量子计算机的关键要求。因此，在利用最先进的量子比特控制和读出技术的同时，可以轻松地操纵和耦合量子比特以实现多量子比特连接的系统是令人感兴趣的。因此，本博士项目将专注于新型锗空穴量子点量子比特的研究，最终目标是实现和扩展空间上分离的量子比特之间的远程耦合。锗中的空穴自旋是一个特别有吸引力的平台，因为它具有快速的操作速度、低的退相干速率和易于制造的特点。该项目将涉及设备设计、建模、测量和特性，并考虑到该架构的扩展。大部分工作将在日立剑桥实验室(HCL)进行，该实验室是该博士的行业赞助商。HCL是基于门的量子比特读出方面的专家，已经在cmos量子比特上做了很多工作。设备将由合作者制造，这些合作者是生长锗结构的领导者。由于HCL在锗量子比特和远程耦合技术方面的设施和专业知识，该项目旨在推进量子比特到量子比特的连接，为可扩展的、通用的量子计算铺平道路。

Quantum processors promise to tackle problems deemed unsolvable by classical computers, advancing fields such as finance, climate change, chemistry and cryptography, amongst others. Current leading platforms for quantum computation include superconducting qubits, ion traps and spins in quantum dots. While there have been many experiments on single-qubit operation in such platforms, two-qubit entangling operations still remain elusive, which are a crucial requirement for realising a useful quantum computer. As such, of interest are systems which can easily manipulate and couple qubits to achieve multi-qubit connectivity, while leveraging state-of-the-art qubit control and read-out techniques.This PhD project will therefore focus on the study of novel germanium-hole quantum-dot qubits, with the end goal of implementing and extending long-range coupling between spatially separated qubits. Hole spins in germanium are a particularly attractive platform due to fast manipulation speeds, low decoherence rates and ease of fabrication. The project will concern device design, modelling, measurement and characterisation, with considerations towards scaling this architecture. The majority of work will be carried out at the Hitachi Cambridge Laboratory (HCL), the industrial sponsor of this PhD. HCL are experts in gate-based qubit readout, with much work already performed on CMOS qubits. Devices will be fabricated by collaborators which are leaders in growing germanium structures. Due to the facilities and expertise in germanium qubits and long-range coupling techniques at the HCL, this project aims to advance qubit-to-qubit connectivity, paving the way towards scalable, universal quantum computation.