Nuclear Nanomagnets for Quantum ComputingInformation technology today involves manipulating and transporting small collections of charges through a system of small wires and semiconductor transistors. Making faster and cheaper computers means making these components smaller - in fact their size is halving every two years, and soon we will reach the limit where transistors are the same size as the atoms themselves! Electrons can be thought of as being like a particle or like a wave, and it is the size of the electron wave that determines its behaviour in such small components. Quantum mechanics, the physics that describes such small systems, predicts that electrons in such small components will have totally different properties, and we will have to design our components in a completely new way.Understanding how to deal with the quantum behaviour of electrons presents us with the opportunity to make a new type of computer. Researchers have shown that a quantum computer is theoretically possible by making use of the purely quantum nature of electrons and light. These quantum computers are still in their very early stages, but one day they will perform calculations that will never be possible with conventional computers. My intended research will involve investigating a new type of architecture for a quantum computer. In a quantum computer, information must be stored and transmitted in a reliable way. I will show that it is possible to store information by putting a single electron into a quantum dot . This is a type of nanoscale semiconductor that can store a single electron, and prevent it from interacting or colliding with other electrons and losing its information. It turns out that the best way to store information in the electron is to encode it into its spin . Spin is the intrinsic magnet of an electron. We can change its direction from up to down , in the same way that bits in a computer have the value 0 or 1 .Electron spin is a very good way to store information in quantum dots, but in fact we cannot store the electron spin forever. The problem is that the electron sits inside a semiconductor, which consists of a lattice of atomic nuclei. Each of these nuclei also has its own intrinsic spin, which the electron feels. The magnetic field from each nucleus is very weak, but eventually the electron spin will change due to these nuclei. In my work, on the other hand, I am going to make use of the nuclei. Generally, the nuclear spins point in all directions, but it is also possible to use the electron to redirect all the nuclei to point in the same direction. There are about 10000 nuclei inside our quantum dot, so aligning them all means that the magnetic field felt by the electron is now very large. The nuclei now have a positive effect on the electron spin. Everything is aligned in the same direction and the electron spin may be stored for extremely long times.Solving the problem of how to store electron spins is no good, however, if we are not able to read out and transport its state to another electron spin to perform a calculation. Fortunately, electrons in quantum dots are able to absorb and emit light, and when they do this they also give the information about their spin to a single photon (a particle of light) which we are able to detect. The only problem is that waiting for the electron to produce a photon takes a long time. To make electrons absorb and emit photons faster, we put them into photonic structures that control how the photons interact with the electrons. In my work I will design photonic structures and techniques that are not only so effective that I will be able to either make a very strong nanomagnet, but also so sensitive that I will detect just a single nucleus. This work will help us to understand not only how to make quantum computers using semiconductors, but will tell us a great deal about how to make these basic interactions work in other systems as well.

The proposed multi-disciplinary project lies at the intersection of three major areas: Mathematical Theory of Nonlinear Waves, Solid Mechanics and Non-destructive Testing of Materials and Structures. The aim of the project is to develop a mathematical theory of nonlinear waves propagating in layered elastic waveguides with extended inhomogeneities representing damage/delamination. This will be achieved using mathematical models of different complexity and the application of a wide range of analytical methods and numerical simulations. Theoretical predictions will be tested experimentally to verify the mathematical theory. Traditionally, nonlinear waves in fluids and solids are studied by different communities of researchers. However, it becomes increasingly clear that there are many analogies in the mathematical approaches to seemingly different problems. One of the best known problems in the area of nonlinear waves in inhomogeneous media is the classical fluid mechanics problem of the dynamics of surface gravity waves propagating over smooth bottom topography. This problem has been studied in various formulations, including monochromatic waves, shallow-water solitons and wave packets. The present project aims at the theoretical and experimental study of nonlinear wave processes in imperfectly bonded layered elastic waveguides with extended interfacial inhomogeneities (modelling poorly bonded areas), which can be considered, in a sense, as an analogue of the classical problem described above. Indeed, we can assume that coupling between the layers varies slowly along a layered waveguide (modelling the areas where the cohesive forces between the layers are weakened by the presence of defects). We can then use the variational formulation of the problem and methods developed for surface gravity waves propagating over variable topography to describe the slow evolution of a nonlinear wave (such as a strain soliton, monochromatic wave or a wave packet). In particular, given the initial velocity of the strain soliton, we expect to be able to find the characteristics of the damaged region sufficient to cause the propagation failure of the soliton. This last effect can be potentially used for the non-destructive testing of layered structures, using nonlinear waves.Note that although similar mathematical methods have already been developed for some classical fluid and solid mechanics problems, their application to the described problem of nonlinear elasticity will be completely new and highly nontrivial.

We propose a Centre-to-Centre consortium formed of 10 academics from the University of Sheffield (USHEF) and the Technical University of Dortmund (TUD) to exploit light-matter interactions in advanced materials, achieving agenda-setting advances in non-linear optics, single photon phenomena and spin-control on the nanoscale. We will study ultra-pure cuprous oxide, atomically thin two-dimensional semiconductors, and III-V semiconductor nano-structures, all at the forefront of modern day research. The collaboration provides major added value to the UK by enabling cutting-edge research themes supported by close interaction with highest quality scientists at TUD, as well as access to their world-leading experimental infrastructure. The interaction of light and matter is at the heart of a huge range of natural phenomena and applications in physics, chemistry, biology etc. In this project, we will use potentially transformative approaches to harnessing these phenomena by using specially designed nano-structured materials, and exploring non-linear and quantum optical phenomena in micro- and nano-photonic structures. The ambition is to seed and develop new research directions based on enhancing and controlling light-matter interactions in nanoscale structures. To this end we will use a broad base of novel materials including atomically thin layers of transition metal dichalcogenides (TMDs), ultra-pure Cu2O, and quantum dots located within III-V semiconductor nano-photonic structures. The consortium will address three inter-related themes having considerable synergy and sharing of techniques and physics including: non-linear and quantum optics with Rydberg exciton-polaritons in cuprous oxide; valley phenomena in van der Waals heterostructures; ultrafast quantum nano-photonics. All three themes involve the harnessing of light-matter interactions in novel material systems. Design on the nanoscale is a common theme throughout enabling the discovery of new optical and quantum-optical phenomena. Furthermore, they all rely on the control of the properties of excitons in extreme limits. As well as leading to ground-breaking new physics, the programme has potential to open up long term applications in quantum communications and in spintronic devices to give just two examples. The highly integrated collaboration programme, exploiting to the full the benefits of the Centre-to-Centre cooperation, will be supported by a total of 60 months of extended visits by postdocs in both directions between Sheffield and Dortmund.