Theoretical Control of Trapped Ions

I have independently found an algorithm for evolving a two-level ion trapped in a harmonic potential cooled to the quantum ground state into any arbitrary target superposition, up to a relative phase difference between the elements. This is done using discrete time-independent pulses of the carrier, first red and first blue sidebands of the internal transition, allowing it to be carried out within the Lamb--Dicke regime without any kind of special pulse-shaping equipment often used in optimal control. On the way to deriving the algorithm, I have investigated some methods and pitfalls in numerical optimisation of pulse sequences, including the limits of double-precision numerics for certain target functions.
I am now working on the optimisation of pulse sequences using time-varying amplitudes of the same transition frequencies to minimise the effects of heating and other decoherence effects to achieve optimal sequences for creating arbitrary motional superpositions. I am also working on creating higher fidelity quantum gates in trapped ions using the Floquet method for pulse shaping. Both of these aims build on work that has previously been done in the controlled quantum dynamics group here at Imperial College London. The Floquet method has found real success in the field of optimal control of quantum systems, allowing for smoothly varying control pulses to be found, rather than the discretised solutions with small time-steps found by algorithms such as GRAPE. Part of my role also involves working closely with the experimental ion trapping group, helping to identify areas of theoretical interest to investigate, and finding solutions to problems that arise when trying to experimentally implement the protocols that the theorists find. I will assist in the setup of new equipment coming into the lab under a new grant, and play a minor role in the building of a new linear rf trap to complement the existing Penning trap. My immediate work with the group is to attempt to experimentally realise the discrete time pulse sequences that I have previously found to form arbitrary motional states in a single trapped ion.

The main impact of the proposed Hub will be in training quantum engineers with a skillset to understand cutting-edge quantum research and a mindset toward developing this innovation, and the entrepreneurial skills to lead the market. This will grow the UK capacity in quantum technology. Through our programme, we nurture the best possible work force who can start new business in quantum technology. Our programme will provide multi-level skills training in quantum engineering in order to enhance the UK quantum technologies landscape at several stages. Through the training we will produce quantum engineers with training in innovation and entrepreneurship who will go into industry or quantum technology research positions with an understanding of innovation in quantum technology, and will bridge the gap between the quantum physicist and the classical engineer to accelerate quantum technology research and development. Our graduates will have to be entrepreneurial to start new business in quantum technology. By providing late-stage training for current researchers and engineers in industry, we will enhance the current landscape of the quantum technology industry. After the initial training composed of advanced course works, placements and short projects, our students will act as a catalyzer for collaboration among quantum technology researchers, which will accelerate the development of quantum technology in the UK. Our model actively encourages collaboration and partnerships between Imperial and national quantum tehcnology centres and we will continue to maintain the strong ties we have developed through the Centre for Doctoral Training in order to enhance our on-going training provisions. The Hub will also have an emphasis on industrial involvement. Through our new partnerships students will be exposed to a broad spectrum of non-academic research opportunities. An important impact of the Hub is in the research performed by the young researchers, PhD students and junior fellows. They will greatly enhance the research capacity in quantum technology. Imperial College has many leading engineers and quantum scientists. One of the important outcomes we expect through this Hub programme is for these academics to work together to translate the revolutionary ideas in quantum science to engineering and the market place. We also aim to influence industry and policy makers through our outreach programme in order to improve their awareness of this disruptive technology.