The discovery of superconductivity under ambient conditions would unlock the full potential of this remarkable phenomenon and allow technological developments that would help solve some of the most pressing and important societal challenges, such as reducing greenhouse gas emissions, transforming health and healthcare, and developing new quantum technologies, all of which are EPSRC research priorities. This experimental research proposal aims to probe the microscopic nature of high-temperature superconductivity in a class of materials known collectively as hydride superconductors and in so doing, will take critical steps towards achieving this important milestone. Electric currents can flow through superconductors without energy dissipation, i.e. without electric resistance, below a critical transition temperature Tc. This unique property is already exploited in medical applications such as MRI and encephalography, while superconducting qubits are considered as one of the most promising platforms for quantum computation. New applications to deliver cleaner energy are also under development. In nuclear fusion reactors (www.tokamakenergy.co.uk), for example, the high magnetic field strengths required to confine the hot plasma can only be produced by superconducting magnets. The main impediment to large-scale exploitation of superconductors in mainstream applications is simply the cost incurred in having to cool them down below Tc. This drives the continual search for better and more robust superconductors. The ultimate quest for room-temperature superconductivity has been one of the most intensely pursued topics in condensed matter physics. Recently, it has reached its peak with the discovery of several superhydride compounds such as H3S and LaH10 synthesised at ultra-high pressures. While near-room-temperature superconductivity has been confirmed in these compounds by a few independent research groups, no microscopic signatures of the superconducting state have yet been reported. Determining the fundamental parameters responsible for room-temperature superconductivity under such extreme pressures will help guide theoretical efforts to identify candidate materials that can support superconductivity under ambient conditions, i.e. at room temperature and at atmospheric pressure. Under the auspices of this Fellowship, I will aim to provide groundbreaking insights into the microscopic nature of the near-room-temperature hydride superconductors. I will develop a set of state-of-the-art experimental techniques, including Raman spectroscopy and tunnelling spectroscopy under extreme conditions of high pressures and high magnetic fields, to deliver quantitative measurements of the superconducting gap amplitude, as well as the energy spectrum of the relevant atomic vibrations and their coupling with electrons; all key parameters in controlling Tc. At the same time, I will work in close partnership with renowned theorists in the field, who will use my experimental inputs in their search for candidate structures and chemical compositions that could replicate the favourable conditions for achieving near-room-temperature superconductivity at lower applied pressures. In this way, progress towards large-scale exploitation of this transformational technology can be made.

The huge progress achieved in the manipulation of quantum systems is opening novel routes towards the generation of realistic quantum-based technology. Notably many counterintuitive manifestations of quantum mechanics are turning to be key features for next generation devices, whose performances will beat those of classical machines. Atom interferometry is a hallmark example of that. According to quantum mechanics particles can behave like waves, showing interference as well as light does. In addition, they are very sensitive to the surrounding environment and they have mass, which make of them extremely powerful sensors for measuring linear accelerations and rotations. Implementing reliable atom interferometers for practical applications is however still challenging. State-of-the-art devices are based on atomic samples which are manipulated while they fall due to gravity inside a vacuum apparatus. These interferometers are currently reaching their ultimate performances being limited by technical issues. Their ultimate sensitivity depends in turn on the time available for the interrogation and on the finite atom number. An immediate solution to improve the sensitivity consists in enlarging the interrogation area, at the expenses of the size of the device, and increasing the atom number, at the expenses of the spatial resolution of the atomic probe. To obtain high sensitivity while maintaining the devices compact, a new generation of interferometers based on trapped and guided atoms is emerging. These devices have several advantages: the atoms do not fall and the interrogation time can be long, the use of BECs guarantees micrometrical spatial resolution, and interatomic interactions allow for the preparation of entangled states surpassing the standard quantum limit set by the finite atom number. New challenges also arise: the effects of the confining potentials and interatomic interactions must be controlled at a metrological level. The proposed project aims at realizing novel BEC-based quantum sensors which will be able to surpass the limitations of current trapped and guided interferometers by combining some of the most powerful manipulation techniques currently available in the field of ultracold atoms (and beyond). The two key elements are the accurate tailoring of the optical potentials by a spatial light modulator, and the control of the interactions. This exceptional experimental control will be assisted by theoretical optimization such as short-cut-to-adiabaticity and optimal control techniques. In most atom interferometers to date, the beam splitters are realized by pulsing two laser beams in Bragg or Raman configuration. We will instead engineer innovative splitters directly integrated into the optical waveguides which confine the atoms. They can operate continuously and without the need of extra laser beams. All the elements of the interferometer (beam splitter, phase accumulation and recombiner) will be integrated into the same device by properly sculpturing one single laser beam. First, a complete Mach-Zehnder operation will be performed with a condensate with tunable interactions. A negligible or weakly attractive value of the interactions will be used to suppress interaction-induced decoherence or create dispersionless wavepackets. As a result, high sensitivities are expected for such interferometer. In a second phase of the project, we will demonstrate a Sagnac-like interferometer with non-interacting condensates propagating in a close circuit. This will realize a guided atom gyroscope whose achievement has been a long-standing goal, and which finds an important application in inertial navigation. Finally, we will generate mesoscopic optical tweezers for realizing a dynamical double-well potential for Mach-Zehnder interferometry. By moving the tweezers apart we will control the coupling between the two wells, and by setting strong repulsive interactions we will produce optimally spin-squeezed states.

European Cave art is one of the most striking examples of Ice Age archaeology and one of the most important sources of information about the belief systems, symbolic behaviour and aesthetic abilities of the earliest known artists. While its specific meaning will probably always remain hotly debated, it is undoubtedly one of the most intimate windows to the cultural past. However, uncertainties about its exact age seriously hamper our understanding of nearly all aspects of cave art, particularly its relationship to the archaeology that is found below ground and which constitutes the majority of the record of Ice Age human behaviour and behavioural change. We will considerably redress this situation by producing one of the largest corpuses of radiometric dates for the core regions of Palaeolithic cave paintings and engravings; Spain, France and Italy. The results will allow us to determine whether Neanderthals created some of the earliest art, or whether it was a behaviour restricted to our own species; and how it evolved thematically and stylistically over time from place to place. Providing reliable dates for particular artistic themes and styles will allow us to relate the changing artistic traditions to the social and behavioural changes that are recorded in the below ground archaeological record. At present it is still not certain when cave art first appeared in Europe. Radiocarbon has been used to provide dates for the organic pigments used in cave paintings, but many of the results remain controversial. Organic pigments may become contaminated by the much older limestone of the walls of caves, or the charcoal used to make a black pigment could have been old at the time the art was made. Furthermore, radiocarbon can only date carbon based pigments, but the majority of early cave art is either engravings with no pigments, or use mineral pigments such as red ochre that is unsuitable for the radiocarbon method. Many engravings and paintings were created directly on, or became overlain by, calcium carbonate layers formed by the same process as stalagmites and stalactites. We can establish when these layers formed by uranium-series dating, a technique that measures the ratio of uranium to its radioactive decay product thorium. By so doing a minimum or maximum age can be calculated for the art, and by measuring enough examples a chronology for the emergence of the art and its subsequent development and spread of different styles can be constructed. In a pilot project we successfully dated 50 carbonate samples from 11 caves in northern Spain, showing that art in this region appeared 20,000 years earlier that was previously thought, and that it appeared in the period in which the last Neanderthals were disappearing and the first modern humans (Homo sapiens) were arriving. These results raised the possibility that Neanderthals created some of the earliest examples of cave art. If true, this would fit with the emerging picture of symbolic use of pigments by Neanderthals, and would raise our understanding of their behavioural and cognitive capacities significantly. To unravel this requires a far more ambitious project, proposed here, since the distribution of the earliest art may help us understand if it arrived in Europe with the first modern humans; whether it was developed by them only later; or indeed whether some of it can be attributed to the Neanderthals. To address these questions we will date cave art associated with datable carbonate layers in 49 caves in the regions where cave art is most abundant; Spain, France and Italy, and produce the largest database of reliably dated cave art so far produced.

Quantum information science promises to revolutionise information and communications technologies (ICT) in the 21st century via secure communication, precision measurement, and ultra-powerful simulation and computation. The realisation of these technologies will massively enhance our ability to secure and process the ever-increasing volumes of information that drives our global economy. The ability to simulate complex systems could one day deliver new materials, pharmaceuticals and solar cells. Photonics is destined for a central role in these future quantum technologies: single particles of light --- photons --- are an ideal system for encoding, processing, and transmitting quantum information. However, the standard approach of encoding one quantum bit (or qubit) of information per photon limits current techniques to small system sizes. At these small sizes these systems are unable to fulfil their tremendous promise. This Fellowship will take a new approach --- encoding much more information per photon --- and thereby realise systems whose performance exceeds that of a conventional computer. This new approach is made possible by the earlier development at Bristol of the field of integrated quantum photonics --- the use of waveguides on silicon chips to generate and guide photons. Because these waveguide chips can be fabricated in a highly parallel way --- much like computer chips --- highly complex waveguide circuits can be relatively easily realised. By propagating many photons in quantum circuits of many waveguides this type of higher-dimensional system promises a 'fast-track' to new applications in communication, precision measurement, imaging processing and simulation.

Quantum information science and technologies offer a completely new and powerful approach to processing and transmitting information by combining two of the great scientific discoveries of the 20th century - quantum mechanics and information theory. By encoding information in quantum systems, quantum information processing promises huge computation power, while quantum communications is already in its first stages of commercialisation, and offers the ultimate in information security. However, for quantum technologies to have as big an impact on science, technology and society as anticipated, a practical scalable integration platform is required where all the key components can be integrated to a single micro-chip technology, very much akin to the development of the first microelectronic integrated circuits. Of the various approaches to realising quantum technologies, single particles of light (photons) are particularly appealing due to their low-noise properties and ease of manipulation at the single qubit level. It is possible to harness the quantum mechanical properties of single photons, taking advantage of strange quantum properties such as superposition and entanglement to provide new ways to encode, process and transmit information. Quantum photonics promises to be a truly disruptive technology in information processing, communications and sensing, and for deepening our understanding of fundamental quantum physics and quantum information science. However, current approaches are limited to simple optical circuits with low photon numbers, inefficient detectors and no clear routes to scalability. For quantum optic information science to go beyond current limitations, and for quantum applications to have a significant real-world impact, there is a clear and urgent need to develop a fully integrated quantum photonic technology platform to realise large and complex quantum circuits capable of generating, manipulating and detecting large photon-number states. This Fellowship will enable the PI and his research team to develop such a technology platform, based on silicon photonics. Drawing from the advanced fabrication technologies developed for the silicon microelectronics industry, state of the art silicon quantum photonic devices will enable compact, large-scale and complex quantum circuits, experiments and applications. This technology platform will overcome the current 8-photon barrier in a scalable way, enable circuits of unprecedented complexity, and will be used to address important fundamental questions, develop new approaches to quantum communications, enhance the performance of quantum sensing, provide a platform for new routes to quantum simulations, and achieve computational complexities that can challenge the limits of conventional computing. This multidisciplinary research programme will bring together engineers, physicists and industrial partners to tackle these scientific and technological challenges.