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

量子处理器有望解决经典计算机无法解决的问题，推动金融、气候变化、化学和密码学等领域的发展。目前领先的量子计算平台包括超导量子比特、离子阱和量子点中的自旋。虽然在这样的平台上已经有很多关于单量子比特操作的实验，但双量子比特纠缠操作仍然难以捉摸，这是实现有用量子计算机的关键要求。因此，我们感兴趣的是能够轻松操纵和耦合量子位以实现多量子位连接的系统，同时利用最先进的量子位控制和读出技术。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分离量子比特之间的远程耦合。由于操作速度快、退相干率低和易于制造，锗的空穴自旋是一个特别有吸引力的平台。该项目将涉及设备设计、建模、测量和表征，并考虑扩展该架构。大部分工作将在日立剑桥实验室（HCL）进行，该实验室是本博士学位的工业赞助商。HCL是基于门的量子比特读出方面的专家，已经在CMOS量子比特上进行了大量工作。这些装置将由在锗结构领域处于领先地位的合作者制造。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.