Quantum Operations and Imaging Using Highly Coherent Scanning Probe Spins

Optically active spin-defects, such as the nitrogen vacancy (NV) centre in diamond, can be used as powerful tools for quantum sensing, magnetic field imaging and quantum computation.

By incorporating NV centres at the tip of solid-state scanning probes, NV centres have been used as sensitive magnetic field sensors with nanoscale spatial resolution. The NV centre can then be scanned over the surface of a magnetic sample and the consequent interaction between the NV centre and the magnetic field can be measured using optical light and resonant microwaves. As well as quantum sensing and imaging, NV centres on scanning tips can be used for the real-
isation of surface-code quantum computation. Scalable quantum computing architectures require the quantum interaction between two or more quantum bits (qubits) to be highly correlated, i.e. the realisation of quantum entanglement. The movable probe would allow the NV centre in the tip to couple near-surface qubits in the sample, entangling them and allowing for the implementation of local quantum operations.

This project will make use of a new operational state-of-the-art scanning and imaging instrument available to us in the London Centre of Nanotechnology. Initially this instrument will be used to image interesting samples to biology and condensed matter physics, such as novel magnetic materials and spin-labelled biological molecules. The stability of near-surface NV centres, as well as possibly silicon carbide defects, will be investigated and the fabrication technique will
be optimised to create defects with superior spin properties. This instrument can also be used to start introductory work on achieving spin-spin coupling and entanglement between donor spins in a material using a movable probe spin.

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.