Towards a Logical Qubit in Silicon: Scalable 2-qubits Operations in CMOS-compatible Quantum Dots

Quantum computing holds the promise to solve intractable problems in various domains, such as drug designs, material science or data prediction. Several hardware platforms are being investigated to host quantum computers, and it is still unclear which scheme will be optimal for computation. Spin qubits in silicon quantum dots are promising candidates given their large qubit density and their compatibility with the silicon-CMOS industry. However, some key building blocks to
achieve a silicon-based quantum computer are still to be demonstrated. In particular, realising coherent control of quantum-dot qubits in a two-dimensional array remains to be shown. This requires careful thinking of architectural elements such as sensors, one-qubit gate and two-qubit gate elements to guarantee coherence along with selective control. For this PhD, we look to construct the first silicon spin qubits array displaying coherent two-qubit gates in the two dimensions of the plane, in devices fabricated in industrial foundry. This will be an essential ingredient to building an error-corrected unit cell of silicon qubits, and will pave the way to industrially-scalable quantum processors. Such project is challenging due to the noisy interaction between the quantum dots defining the qubits, enhanced when increasing the dimensions of the qubit array. This PhD will build on the expertise of Prof. John Morton's research group on sensing and controlling
silicon spin qubits in linear arrays, with the aim to achieve coherent control of entanglement in 2D spin qubits array.

The first and most important impact of our Centre will be through the cross-disciplinary technical training it provides for its students. Through this training, they will have not only skills to control and exploit quantum physics in new ways, but also the background in device engineering and information science to bring these ideas to implementation and to seek out new applications. Our commercial and governmental partners tell us how important these skills are in the growing number of people they are hiring in the field of quantum technologies. In the longer term we expect our graduates to be prominent in the development of new technologies and their application to communication, information processing, and measurement science in leading university and government laboratories as well as in commercial research and development. In the shorter term we expect them to be carrying out doctoral research of the highest international quality.

Second, impact will also flow from the students' approach to enterprise and technology transfer. From the outset they will be encouraged to think about the value of intellectual property, the opportunity it provides, and the fundraising needed to support research and development. As students with this mindset come to play a prominent part in university and commercial laboratories, their common background will help to break down the traditional barriers between these sectors and deliver the promise of quantum technologies for the benefit of the UK and world economies. Concrete actions to accelerate this impact will include entrepreneurship training and an annual CDT industry day.

Third, through the participation it nucleates in the training programme and in students' research, the Centre will bring together a community of partners from industry and government laboratories. In the short term this will facilitate new collaborations and networks involving the partners and the students; in the long term it will help to ensure that the supply of highly skilled people from the CDT reaches the parts of industry that need them most.

Finally, the CDT will have a strong impact on the quantum technologies training landscape in the UK. The Centre will organise training events and workshops open to all doctoral researchers to attend. We will also collaborate with CDTs in the quantum technologies and related research areas to coordinate our efforts and maximise our joint impact. Working in consort, these CDTs will form a vibrant national training network benefitting the entire UK doctoral research community.