Sunlight penetrating into the ocean is the ultimate source of energy in oceanic ecosystems. This energy sustains fisheries and catalyses biogeochemical cycles that influence the carbon cycle and ultimately climate. Single-celled photosynthetic organisms termed phytoplankton are the gatekeepers of this energy flux, achieved via the absorption of light by photosynthetic pigments such as chlorophyll. However, the range of processes in the cell that determine how this light energy is subsequently used to support growth and survival of these crucial organisms are not well characterised. This 'knowledge gap' is a result of the current paradigm that mainly considers photosynthesis in terms of the amount of 'carbon fixed' rather than 'energy captured'. Here we propose that natural phytoplankton taxa are more adaptable in their energetic metabolism than currently assumed, using different 'molecular strategies' to specifically power a range of critical cellular processes beyond carbon fixation. These different strategies potentially represent more than half of photosynthetic energy flux in many circumstances. The corresponding diversity of metabolic strategies is thus likely to represent a fundamental process through which these crucial organisms adapt to thrive across different ocean ecosystems. We will obtain an improved understanding of how phytoplankton use light energy in ocean systems, which is critical to our ability to understand how oceanic ecosystems operate and thus predict how the ecosystem services they provide (including sustaining fisheries, sequestering atmospheric CO2 and producing other climate reactive gases) may change as the global system evolves. For example, we currently use satellites to measure the colour of the ocean and hence estimate phytoplankton abundance and infer rates of primary production without a full mechanistic understanding of how these phytoplankton use the available light energy. Such understanding of the coupling of light energy capture to cellular survival, growth rate and carbon fixation is crucial for facilitating better estimates of primary production and ultimately understanding the key role of the oceanic biota in the global carbon cycle. To achieve this, we propose an observational and experimental program that will define how diverse phytoplankton communities use light energy over natural gradients in nutrient and light availability. We will undertake a research cruise encompassing the South Atlantic, as well as the iron-limited regions of the Southern Ocean, to sample natural phytoplankton communities at sea. These will be analysed to determine their rates of photosynthesis and, through molecular functional and community structure analysis, to define the processes involved in harvesting and using photosynthetic energy. The information from the natural community experiments will be extrapolated to a larger scale via network analysis and mapping approaches to generate a global understanding of how cells use light energy. Our deliverables will be an observationally and experimentally derived integrated view of the environmental and physiological controls on how phytoplankton in ocean systems actually use light energy to power all cellular processes (beyond only considering carbon fixation) (OB1 and OB2), and a global-scale synoptic synthesis of where and when different photosynthetic strategies are used by phytoplankton (OB3). We expect this to move the paradigm away from the 'carbon-centric view' to more fully consider the potentially >50% of phytoplankton light energy usage that powers the metabolisms of the organisms underpinning the productivity of ocean ecosystems.

A quantum computer is a machine built to use the mysterious principles of quantum mechanics to achieve an advantage in some task over any standard ("classical") computer. Large-scale quantum computers have not yet been built; however, an international effort is currently underway to do so. Much theoretical work has also been carried out to understand the power of quantum computation, and in particular, quantum algorithms have been developed for certain problems that outperform any possible algorithm running on a classical computer. These problems include breaking cryptographic codes (such as the RSA code which underlies Internet security), certain database search problems, and efficient simulation of quantum mechanical systems (with applications including design of medicinal compounds and novel materials). One reason that the study of quantum computing is so fascinating is that, as well as having practical applications like this, it enables us to obtain a deeper understanding of nature. As it appears that quantum mechanics is the physical theory on which our universe is based, understanding what a quantum computer can do is nothing less than understanding the computational power of the universe. This project aims to find a deeper understanding of what it is about certain problems which means that there is an efficient quantum algorithm to solve them. In particular, the project will develop new algorithms and protocols for quantum computers to obtain dramatic efficiency improvements over classical computation. Some of these algorithms could be tested experimentally in the near future. The proposal is divided into three themes. The first theme will find new quantum algorithms, communication protocols and data structures. For example, super-efficient quantum algorithms will be developed for determining whether an object has some property, or is very far away from having that property. One problem of this nature would be to determine whether a computer network is connected or very far from connected, by looking at only a few, randomly chosen, links between computers. It is by now fairly well understood which problems like this have fast solutions on a classical computer. However, quantum computers might be able to achieve dramatic speed-ups for certain problems of this type. Efficient algorithms for discrete problems (e.g. concerning graphs and codes) will also be developed using the exciting new technique known as quantum walks, and finally the question of whether there exist quantum data structures which are more efficient than any classical data structure will be attacked. In the second theme, ideas from quantum computing will be used to study the complexity of problems from quantum physics and quantum chemistry. On the one hand, new quantum algorithms will be developed that allow quantum computers to solve practically important problems from these fields more efficiently than is possible classically. On the other, intractability of certain problems in this area will be proven, which will enable practitioners (such as physicists and chemists) to determine when problems they want to solve are actually intrinsically hard. Ideas from quantum computing are thus a helpful tool even without having access to a large-scale quantum computer. Finally, the third theme will develop new underlying mathematical technology in order to solve the difficult problems thrown up by the first two themes. These include developments in the theory of "hypercontractivity", which has recently been an essential tool in many important results in theoretical computer science, and new mathematical techniques to find tighter bounds on the abilities of quantum computation. Taken together, these results will mark a significant leap forward in our understanding of the power of quantum computers.