Dopant-based Quantum Technologies in Silicon

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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).