Robust high-fidelity entangling gates using long-wavelength radiation for quantum computation

Quantum computing is a developing field that promises to solve problems which are too hard for a classical computer. However, solutions for these problems can only be found if a fault-tolerant quantum computer is used. The resources needed for such a device are a large number of qubits that can reliably store information and high-fidelity quantum gates to execute the computation.

Furthermore, to be able to reliably perform operations, error correction protocols should be implemented. It was proven that this can be achieved in the presence of limited noise, which imposes a constraint on the lower limit for the gate fidelities, the error thresholds range between 10-4 and 10-2, depending on the noise model used. Error correction protocols use multiple physical qubits to encode a logical qubit, which will be used as the unit employed in computation. Consequently, there is a trade-off between the number of physical qubits necessary for computation and the gate fidelity: the higher the fidelity, the smaller the number of additional qubits needed to compensate for the gate-errors. Considering and overcoming these challenges will enable the implementation of quantum algorithms.

The proposed project will research techniques that can be used to implement entangling gates and increase their fidelity, speed and overall robustness. This will require to reduce the effect of noise sources on the gate functionality, which can lead to designing modifications to the hardware setup. Once these improvements have been made, the project will focus on demonstrating quantum algorithms. A parallel project that will be completed alongside the experimental work is the automation of the conducted experiments. This will enable the hardware used to be remotely accessible and it is a stepping stone towards making the system available to be used in solving different problems.

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.