Two-qubit interactions in two spatial dimensions in silicon

Quantum computing platforms that aim to become fault-tolerant via the use of quantum correction protocols require high qubit connectivity. For the surface code, the most forgiving quantum error correction protocol, qubits will need to interact controllably with nearest neighbours located in a two-dimensional array.

In this PhD project, you will work towards demonstrating for the first time two-qubit interactions in two spatial dimensions in silicon spin qubit devices. Electron spin qubits in silicon are consolidating their position as a leading candidate to build scalable high-fidelity quantum processors since several recent demonstrations have shown single- and two-qubit gate fidelities exceeding the requirements for fault tolerant thresholds. However, all devices up to now have shown interactions only in 1d. In this PhD project, you will design and validate industry-manufactured silicon devices that will allow you to use spin-spin exchange interaction between neighbour spins in a 2d array to implement two-qubit gates in silicon. A positive outcome of this project will facilitate the development of fault-tolerant silicon-based quantum processors.

Our main impacts will be:
- a new generation of interdisciplinary nano researchers with expertise across science and innovation, fluent in the combination of approaches and technologies
- strategic developments in the study and control of nano-interfaces connecting complex architectures, for advances in emerging scientific grand challenges across vital areas of energy, health and ICT
- integration of new functional nanotechnologies together by harnessing nano-interfaces within larger application systems, and their translation into innovative products and services through our industry partners and student-led spin-outs
- a paradigm change of collaborative outlook in this science and technology
- a strong interaction with stakeholders including outreach and public engagement with cutting edge nano research
- improved use of interdisciplinary working tools including management, discipline bridging and IT

Economic impact of the new CDT is focused through our industrial engagement programme, as well as our innovation training. Our partner companies include - NPL, Hitachi, Oxford Nanopore, TWI, ARM, Eight19, Mursla, Britvic, Nokia Bell Labs, IBM, Merck, Oxford Instruments, Aixtron, Cambridge Display Technologies, Fluidic Analytics, Emberion, Schlumberger, Applied Materials and others. Such partnerships are crucial for the UK to revive high value manufacturing as the key pillar to lead for future technologies. We evidence this via the large number of CDT projects resulting in patents, with their exploitation supported by Cambridge Enterprise and our Industry Partners, and direct economic impact has also resulted from the large proportion of our students/alumni joining industry (a key outcome), or founding startups including: Echion Technologies (battery materials), Inkling Cambridge (Graphene inks and composites), HexagonFab (2D materials), Simprints (low-cost biometrics), Cortirio (rapid diagnosis of brain injury).

Training impact emerges through not just the vast array of Nano techniques and ideas that our cohorts and associated students are exposed to, but also the interdisciplinary experience that accrues to all the academics. In particular the younger researchers coming into the University are plugged into a thriving programme that connects their work to many other sciences, applications, and societal challenges. Interactions with external partners, including companies, are also strong and our intern programme will greatly strengthen training outcomes.

Academic impact is fostered by ensuring strong coherent plans for research in the early years, and also the strong focus of the whole CDT on study and control of nano-interfaces connecting complex architectures. Our track record for CDT student-led publications is already strong, including 4 Nature/Science, 6 Nature Chem/Nano/Mat, 13 Nat. Comm., with student publications receiving >6000 citations in total, including 16 papers with >100 citations each and high altmetric scores. Students have also given talks and posters at international conferences and won numerous awards/fellowships for research excellence.

Societal impacts arise from both the progression of our cohorts into their careers as well as their interaction with the media, public, and sponsors. We directly encourage a wide variety of engagement, including interaction with >5000 members of the public each year (mostly pre-university) through Nano exhibits during public events such as the Cambridge Science Festival and Royal Society Summer Science Exhibition, and also art-science collaborations to reach new audiences. We also run public policy and global challenges workshops, and will further develop this aspect with external partners. Our efforts to bring societal challenges to students' awareness frames their view of what a successful career looks like. Longer term societal impact comes directly from our engagement with partner companies creating jobs and know-how in the UK.