Problems during birth leading to a lack of oxygen (birth asphyxia) and subsequent brain injury (neonatal encephalopathy or NE) occur in 1-2 per 1000 full term births in the UK. An infant's health is in great danger when there is a prolonged lack of oxygen delivery to meet the metabolic demand of the brain. Perinatal brain injury remains a significant cause of neonatal mortality and is associated with long-term neurological disabilities including cognitive impairment, mental retardation and accounts for 15 to 28% of children with cerebral palsy. Monitoring the tight balance of brain blood flow, oxygen delivery and brain tissue metabolic rate is a major aim in patient diagnosis and care. Clinicians currently cannot monitor the biochemical status of theinjured brain continuously and non-invasively at the infant's cot-side. There is an urgent clinical need to detect as early as possible those neonates at most risk and who may benefit from adjunct therapies and/or redirection of clinical care for effective rehabilitation. Early detection and assessment of brain neurological status and outcome requires sensitive, robust and easy to measure biomarkers. We are proposing to take a new and creative approach to the way in which the neonatal brain is monitored and useful information is delivered to doctors. We will first develop an entirely novel portable, non-invasive brain monitoring instrument, which will allow birth asphyxiated infants to be monitored at the cot-side in the intensive care unit. This will open up new possibilities for how we guide the management of babies with brain injury. This new instrument will be based on integrating two technologies that use light to monitor the brain. The first technique is broadband near-infrared spectroscopy (or broadband NIRS) and uses low light levels of near-infrared light to measure the distribution of oxygen and blood in the brain, and how oxygen is being utilised by mitochondria the power factory of cells. The second technique is called diffuse correlation spectroscopy and uses a single wavelength (colour) of near-infrared laser light to measure the movement of the red blood cells and hence quantify brain blood flow. In particular this instrument will be able to monitor non-invasively brain blood flow, brain oxygen levels and the metabolic status of the brain tissue by measuring the electrochemical status of cytochrome-c-oxidase, an enzyme in the mitochondria. We will evaluate this instrument and measurement in the lab using a large animal model of the human neonate; after which we will move on to clinical evaluation studies in the neonatal intensive care unit. The system/instrument will be specifically designed to help doctors to quantify the injury severity and optimise the type and duration of therapies, minimise the risk of further injury to the brain, and thus improve the likelihood of the infant's recovery. In addition to building this new neuromonitoring instrument, we will also develop computer programmes which are essential to extract the relevant information from the measured signals from the brain. This will involve developing routines for delivering measurements in real time, and incorporating a computer model of the brain to help us understand the meaning and relationships of our measured signals. We have a long and successful track record of this type of translational research, i.e. the combined approach of hardware and software engineering of novel brain imaging technologies targeted at specific applications in healthcare, and introduction into clinical use. We have assembled a multidisciplinary team to meet the challenges of this ambitious project including engineers, clinicians and physicists, and we have attracted the interest of an industrial project partner for potential commercial exploitation of our developed systems.

Quantum information science is the field of research that studies the information present in a quantum system. It opens the way to the knowledge of unexplored fundamental physical mechanisms and to the development of novel technologies that will profoundly transform the way we communicate and process our data. Indeed, a number of new technological applications can be envisaged thanks to exquisitely quantum phenomena. While classical information encoding relies on bits, which can be either 0s or 1s, the quantum bits (or qubits) are associated to the state of quantum objects, e.g., single atoms, single spins, or single photons. Because of the quantum superposition principle, the qubits can then be 0s, 1s, or coherent superposition of both, thus giving access to an exceptionally richer alphabet. Quantum information science also exploits quantum entanglement, i.e., strong correlation between quantum objects, as a resource for fast and secure quantum communication protocols. In view of realizing networks for quantum communication, quantum memories are fundamental devices as they act as interfaces between the photons, used as information carriers (or flying qubits), and stationary qubits, exploited for information storage and processing. While atomic gases enabled the first remarkable quantum storage experiments, solid-state systems, and specifically rare earth ion doped crystals, also offer interesting perspectives thanks to the absence of atomic motion and the high density, and the fact that they unleash prospects of integration, which facilitates scalability and employability in real-life quantum technology demonstrations. As a matter of fact, the implementation of quantum information protocols on a small chip has the potential to replicate the revolution of modern electronic miniaturization and intense research efforts are indeed devoted to developing miniaturized photonic integrated circuits for quantum information processing. Yet, on chip memories for single photons, key components of future quantum communication technology, are currently missing. This Fellowship addresses this pressing challenge by developing waveguide quantum memories based on ultrafast laser micromachining of rare earth ion doped crystals. We will engineer the necessary tool kit for the integrated quantum memories to fulfil simultaneously all the requirements for their employability in real-life quantum networks, as on-demand read-out, high efficiency, long storage time, and multimodality. Moreover, we will demonstrate how the integrated design gives access to functionalities that are not possible with bulk devices, like the non-destructive detection of single photons. This vision represents a technological breakthrough toward the realization of complex memory-enhanced quantum photonics circuitry on chip.

The theoretical description of matter in strong laser fields is a rather challenging task. This is due to the fact that the external laser field is comparable to the atomic binding forces, and the usual theoretical methods considered in optical physics, such as perturbation theory with the laser field, are not applicable. In particular, it is very difficult to apply analytical or semi-analytical methods to such a physical framework. There exists, however, one such method, namely the Strong-Field Approximation. This method has served to establish the main paradigms in strong-field laser physics, and has been employed in over 500 publications in this field of research. In particular, it is very powerful for studying quantum interference effects in detail. This approximation suffers, however, from severe drawbacks, which are particularly critical for molecules and systems involving more than one electron. Such systems can not be described by such an approximation in a satisfactory way, and indicate that new, radical ideas are necessary in order to develop the theory further. In this project, we intend to bring ideas and methods from quantum-field theory and mathematical physics to strong-field laser physics to develop a new semi-analytical approach which replaces such an approximation. As a testing ground, we will use such a theory to describe molecules in strong laser fields, and, simultaneously, make a rigorous assessment of the limitations of the Strong-Field Approximation. Such systems have been chosen not only due to their critical behavior, but also due to the fact that, nowadays, there exists pioneering experiments in Britain, at the Imperial College, involving molecules, which will pave the way towards dynamic measurements of matter with a never-imagined precision. This will not only be important for the specific physical systems above, but will revolutionalize a whole area of research.

Nanoscale quantum optics is a promising new field aimed at coherent control and manipulation of single photons emitted by individual quantum emitters in a nanostructured photonic environment. Single emitters have dimensions much smaller than the wavelength of light, and therefore interact slowly and omni-directionally with radiation, placing limits on photon absorption and emission. These intrinsic fluorescence limits can be overcome when the source is placed in a nanostructured photonic material. Multi-scale (fractal) structures are a new class of particularly interesting photonic materials, since they lead to spatial localisation of the electromagnetic energy into subwavelength areas (hot spots of 10s of nm) over a wide spectral range, which are driven by optical excitations coupled to the network on different scales. Here I propose to investigate collective plasmonic systems, based on plasmon multiple scattering and interference on metallic networks. I will study natural gold networks and artificially designed one. I will approach these structures using a network theory approach, a statistical method centred on the network topology, made of links and nodes. This method has the potentiality of describing the complex system with few robust parameters, extracted from the rich microscopic details, and thus provides much deeper understanding. The study of network optical properties will focus on probing one of the most robust modal properties: the local density of optical states. This is a key fundamental quantity involved in light-matter interaction, as it provides a direct measure for the probability of spontaneous light emission (the Purcell effect), light absorption and scattering. I propose to identify the emergent nature of the different optical modes of complex plasmonic networks by studying the statistics of the LDOS in artificial plasmonic networks. I plan to understand the inner character of the complex plasmonic modes, and to reveal subwavelength "hot-spots", critically localized states and chaotic mode signatures. This knowledge will be exploited to design and engineer the LDOS for local fluorescence enhancement and to exploit the network as an unconventional antenna to control the fluorescence of an individual colloidal quantum dot, enhance its radiation rate, boost and manipulate its directionality. I will aim at demonstrating a strong link between the plasmonic network structures, their optical properties and their effect on a light emitter.

This project is targeted at establishing the fundamental limits of quantum interferometry, with particular emphasis on the specific and widespread Hong-Ou-Mandel (HOM) interferometer. We will show that quantum HOM interferometry enables extremely precise depth and thickness measurements in an optical microscope. We then propose to use this approach to build a non-invasive optical imaging system that will provide sub-nanometer precision, improving upon the state-of-the-art by three orders of magnitude. To achieve our goal, we will combine customised quantum optical interference with new advanced statistical analysis tools. We will also integrate the latest ultra-sensitive single-photon detector array sensors into the imaging system to provide unprecedented sensitivity and temporal resolution. This interdisciplinary research brings together experimental and theoretical physicists to develop the optical systems, sources and underlying models, and biologists as end users of the technology. Our research relies on quantum interference of indistinguishable single photons, known as Hong-Ou-Mandel interference, which can give very precise information about the thickness of an unknown sample. The principle works by using two identical photons, which are produced at exactly the same time. If one of the photons is delayed with respect to the other due to transmission through a sample of unknown thickness, the properties of the sample can be established by detailed analysis of the interference pattern when the two photons are brought back together. Furthermore, the precise form of the interference pattern, and consequently the precision of the measurement, can be controlled by customising the spectral properties of the single photons. Generally, this method provides high temporal precision with a large dynamic range, yet does not suffer from phase instability between the two photons. While this phenomenon has been known for many years, the tools to reach its fundamental limits have not yet been developed. To reach the boundaries of this optical method, we will develop custom photon sources to provide tailored quantum interference patterns and develop new analysis procedures based on the Fisher information associated with the data. The Fisher information is a statistical approach for assessing how much information about an unknown parameter is available in measured data. In any physical system, one builds a model that includes a number of parameters, and in our imaging system, the thickness of the sample will be the key quantity that we wish to establish. Small changes to the thickness of the sample will result in small changes to the observed data and by analysing the Fisher information, we will be able to reach the ultimate precision provided by information theory. We predict this ultimate limit to be sub-nanometer in precision. In the final stages of the project, we will also measure a series of biological samples. Accurately establishing cell, protein, and DNA morphology is vital for determining the performance of biological systems. It is well known that the structural form of DNA plays a crucial role in its functionality. DNA can be prepared in various forms and can take the shape of strands or more convoluted structures, such as for example DNA origami. The DNA strands therefore occupy different volumes and thicknesses at the nanometer level. After metrology of defined 'ground truth' DNA origami structures, we will extend our study to that of chromatin structures in vitro.