Dopant-based Quantum Technologies in Silicon

量子技术在过去十年中取得了长足的发展，现在有几种材料平台可以操作少量量子位；例如那些基于捕获离子、超导或半导体材料的技术。其中，目前最有前途的量子比特实现之一是硅中的掺杂自旋。硅中电子和核自旋的相干时间通常分别超过几毫秒和几秒钟。与此同时，硅平台受益于能够建立在半导体行业的专业知识和制造设施之上。然而，使用半导体材料作为固态量子比特的平台有其独特的挑战，甚至不同于最先进的经典硅技术。例如，与经典电子学中的半导体芯片不同，自旋量子位对最小的磁场波动都很敏感，对通过自旋-电荷耦合途径（如自旋轨道或交换耦合）产生的电荷波动很敏感，并且通常需要在低温下操作。要将硅中的掺杂自旋发展成为一种可行的、可扩展的、有益于社会的技术，仍然需要学术界和工业界合作伙伴的一系列步骤改变和持续投资。因此，在这里，我们将汇集来自英国和海外大学的人才网络，以及许多行业合作者，他们非常适合应对这些挑战。在我们的人员网络带来的关键能力中，首先是制造具有原子精度（UCL）的掺杂器件的能力。在国际上，拥有这种专业知识的团队很少，在某些方面，例如在硅中掺入砷掺杂剂，我们的专业知识确实是独一无二的。为了评估这些器件，需要mK传输测量来建立关键指标，如量子相干性和门保真度。在这里，我们汇集了几个在这方面有长期记录的小组（伦敦大学学院，悉尼），以及在基准测试和量子纠错方面所需的理论基础（悉尼，麦吉尔）。尽管如此，为了充分理解设备性能，理解和准确地描绘出任何传统技术都无法实现的能量和空间分辨率的量子设备的性能是至关重要的。在我们的网络中，我们有能力将传输测量与器件的mK扫描门映射（剑桥）和纳米尺度上的单电子灵敏度（麦吉尔）结合起来。这项工作将集中在两个工作包中，第一个工作包侧重于构建所需的量子位制造和器件结构，而第二个工作包将侧重于在物理分离的量子位之间创建纠缠。将这些关键能力和研究成果结合到一个单一的网络中，使我们能够在量子器件开发和表征方面大大超越当前的技术水平，从而可以建立可靠和可行的原型。除了第一个原型之外，该网络还将致力于平台的可扩展性，包括设备制造（UCL）和所需的经典低温控制电子设备（悉尼）。另一个好处是，研究小组在数据采集、材料表征以及硬件和软件开发方面与行业领导者紧密结合。为了确保我们的研究能够接触到广泛的受众，并为所有相关利益相关者提供服务，我们将有一个专门的外展计划（悉尼领导）。

Quantum technologies have seen considerable development over the last decade and there are now several material platforms available in which a small number of qubits can be operated; such as those based on trapped ions, superconducting, or semiconductor materials. Of these, one of the most promising current qubit implementations are dopant spins in silicon. The coherent times of electron and nuclear spins in silicon routinely exceeds milliseconds and seconds, respectively. At the same time, the silicon platform benefits from being able to build on the expertise and fabrication facilities of the semiconductor industry. Nevertheless, using semiconductor materials as a platform for solid-state qubits comes with its own unique challenges that are different from even state-of-the art-classical silicon technology. For example, unlike semiconductor chips found in classical electronics, spin qubits are susceptible to even the smallest magnetic field fluctuations, are sensitive to charge fluctuations via spin-to-charge coupling pathways such as spin-orbit or exchange coupling, and typically require operation at cryogenic temperatures. To develop dopant spins in silicon into a viable and scalable technology that would benefit society still requires a number of step changes and sustained investment from academic and industry partners. Here, we will therefore bring together a network of people from both UK and overseas universities, as well as many industry collaborators, which are uniquely suited to address these challenges.Of the key capabilities that our network of people brings, the first is the ability to fabricate dopant devices with atomic precision (UCL). Internationally there are very few groups with this expertise, and in some aspects, such as the incorporation of As dopants in silicon, our expertise is truly unique. To assess the devices requires mK transport measurements to establish key metrics such as quantum coherence and gate fidelities. Here we bring together several groups (UCL, Sydney) which have a long track record in this regard, as well as the required theoretical underpinning in terms of benchmarking and quantum error correction (Sydney, McGill). Still, for a full understanding of the device performance it is essential to understand and, quite literally, map out the performance of the quantum devices with energy and spatial resolution not possible with any conventional technology. In our network, we have the capability to combine the transport measurements with mK scanning gate mapping of the device (Cambridge) and single-electron sensitivity on the nm scale (McGill). The work will be brought together in two work packages, the first focussing on building the required qubit fabrication and device structures, whereas the second work package will focus on creating entanglement between physically separated qubit.Combining these key capabilities and research efforts into a single network allows us to go significantly beyond the current state of the art in terms of quantum device development and characterisation such that reliable and viable prototypes can be built. Looking beyond the first prototypes the network will also be working on the scalability of the platform, both in terms of device fabrication (UCL) and the required - classical cryogenic - control electronics (Sydney). An additional benefit is that the research group is strongly integrated with industrial leaders, in terms of data acquisition, materials characterisation and hardware and software development. To ensure our research will reach a wide audience and be available to all relevant stakeholders we will have a dedicated outreach programme (Sydney lead).