From the earliest invention of the camera, humans have been seeking to observe processes that are too fast or too complex for the human eye to follow. The first time-lapse images of a running horse, taken by Eadweard Muybridge in the 19th century, allowed us to understand its motion, freezing a moment in time so that we can examine minute details. It showed that a horse's feet all leave the ground when galloping, a controversial question hotly debated at the time. Importantly, the time lapse images were a full-frame view - a key concept which we will also employ in the instrument to be developed here. Today, in cellular biology, our understanding of cellular function continues to evolve as we observe complex dynamic processes played out under a microscope. The optical microscope is a non-invasive, non-destructive and non-ionising tool which can be used to study living cells and tissues. No other method can study molecules in living cells with anything remotely approaching its combination of spatial resolution, selectivity, sensitivity and dynamics. Modern sensitive and sophisticated electronic cameras can capture dynamic processes at high speed, revealing intricate details of these processes. Indeed, detector development is a very important aspect of progress in the field of microscopy. The aim of our project is to develop extremely sensitive and fast full-frame view cameras which will allow us to observe molecules and proteins in their natural habitat, the cell, without disturbing them - in a way the 21st century equivalent of Muybridge's galloping horse. We are interested in molecules that play a role in inflammation, which is the body's response to some kind of harm or injury. These molecules are called proteins, and they are many different ones in our cells. We specialise in finding out about a protein called the coxsackie virus adenovirus receptor (CAR). We want to know how they move around in time, bump into each other and stick together. So we have labelled them with a fluorescent label to observe them under a microscope. The special cameras we are going to develop will be able to see them with a very high resolution, and also very quickly and very precisely, by measuring the polarization of the fluorescence emitted by its label. They will allow us to observe the moment a cell responds to a chemical stimulus at the level of single proteins. This will help us to understand how inflammation occurs, on a molecular basis - which, at the moment, is still unknown. Imaging living cells is the best available approach to study this kind of biological question, and others, and, ultimately, the knowledge and insight gained by doing this work will enable us to design and develop drugs against inflammation, for the benefit of all of humankind.

The accurate tracking of medical devices is a key clinical requirement that currently requires the use of ionising X-ray radiation and / or contrast agents. These essential procedures have potential long term detrimental effects, especially on babies, and also causes significant disruption (and therefore cost) due to both the need to protect staff and waiting for the availability of, or transport to, X-ray equipment. There are therefore significant clinical drivers to develop alternative tracking methods. Very recently, we have demonstrated a ground breaking approach to tracking medical devices located deep in tissues using single photon imaging [1]. Our approach exploits the fact that if a point source of light is placed inside the body, a tiny fraction of the light will emerge from the body with a close to line-of-sight path. Crucially, these line-of-sight photons (particles of light) hold precise information about the spatial location of the point source inside the tissue, but extracting this information is not trivial. The key to accessing it is the fact that the line-of-sight photons exit the body with a shorter transit time than the more diffuse photons - a fact that allows us to exploit a technique known as time-correlated single-photon counting (TCSPC) to detect and distinguish them from more diffuse photons. In contrast to "normal" cameras, which do not record the arrival time of the photons on the detector array, TCSPC-based imaging relies on using a source of light that produces short pulses of light at precisely known times, together with a single-photon sensitive detector array that can record the arrival times of individual photons. In this manner, TCSPC imaging allows us to design an imaging system that can selectively detect and image the location of the emerging line-of-sight photons before the diffuse photons start to emerge, and this allows us to locate the precise position of the source. Although we have now demonstrated the potential of this technique for medical device tracking, the clinical translation has been hampered by the low fill-factor (how much of the detector array is light-sensitive) of commercially available TCSPC detector arrays. This low fill-factor (~1%) effectively means that we lose 99% of the light reaching the detector array, limiting the maximum frame rate to ~0.05 Hz - too low to provide adequate feedback to the clinician during catheter placement. Recently, through STFC funding, we have demonstrated that so-called "photonic lantern" transitions provide a new and powerful route to addressing the low fill-factor of commercially available SPAD arrays [2]. The overarching goal of this project will therefore be to work with our commercial partners, Photon Force, to exploit this capability, and develop a TCSPC system capable of tracking catheters with video frame rates. We will then work with clinician scientists to translate the technology towards clinical exploitation by demonstrating the tracking capability using relevant models. The results of this project will then be used to support translational clinical studies, and to work with Photon Force to develop a TCSPC tracking system suitable for the medical market. [1] M. G. Tanner et al, Biomed. Opt. Express 8, 4077-4095 (2017) [2] H. K. Chandrasekharan et al. Nat. Commun. 8, 14080 (2017).

We have seen rapid development and growing interest in quantum technologies-based applications in the past decade and the overall global quantum technology market is expected to reach $31.57B by 2026. Most of these emerging quantum applications require single-photon avalanche diode (SPAD) detectors operating beyond the spectral range of silicon but with "silicon-like" performance. The use of "silicon-like" short-wave infrared (SWIR) SPAD detectors in the existing systems will immediately improve resolution and acquisition time for the existing imaging system and enhance the range and improve data rate for Quantum Key Distribution (QKD). However, the present commercially available InGaAs/InP based SPADs based on designs from more than two decades ago are unlikely to have a step change in their performance. Over the last five years, the advent of several innovations by way of novel III-V materials and semiconductor band structure engineering offers us the possibility of a paradigm shift in the performance of long wavelength detectors. The next revolution in the development of SPADs in the SWIR region will almost certainly be using novel materials and band structure engineered structures. Such a revolution will significantly enhance detection efficiency and fast timing. This new class of detectors will be evaluated on existing state-of-the-art testbeds for time-of-flight ranging/depth imaging and QKD. This Fellowship proposal has the ambition to sweep away the obstacles of material and processing problems that are hindering the development of affordable and easy operation SPADs, and to bridge gaps between material sciences, semiconductor physics, manufacturability and quantum technology applications in order to improve the scope and overall performance of next generation quantum technology-based applications.

Quantum physics describes how nature links the properties of isolated microscopic objects through interactions mediated by so-called quantum entanglement and that apply not just to atoms but also to particles of light, "photons". These discoveries led to the first "quantum revolution", delivering a range of transformative technologies such as the transistor and the laser that we now take for granted. We are now on the cusp of a second "quantum revolution", which will, over the next 5-10 years, yield a new generation of electronic and photonic devices that exploit quantum science. The challenge is to secure a leadership position in the race to the industrialisation of quantum physics to claim a large share of this emerging global market, which is expected to be worth £1 billion to the UK economy. QuantIC, the UK's centre for quantum imaging, was formed over four years ago to apply quantum technologies to the development of new cameras with unique imaging capabilities. Tangible impacts are the creation of 3 new companies (Sequestim, QLM and Raycal), technology translation into products through licencing (Timepix chip - Kromek) and the ongoing development with industry of a further 12 product prototypes. Moving forward, QuantIC will continue to drive paradigm-changing imaging systems such as the ability to see directly inside the human body, the ability to see through fog and smoke, to make microscopes with higher resolution and lower noise than classical physics allows and quantum radars that cannot be jammed or confused by other radars around them. These developments will be enabled by new technologies, such as single-photon cameras, detectors based on new materials and single-photon sensitivity in the mid-infrared spectral regions. Combined with our new computational methods, QuantIC will enable UK industry to lead the global imaging revolution. QuantIC will dovetail into other significant investments in the Quantum technology transfer ecosystem which is emerging in the UK. The University of Glasgow has allocated one floor of the £118M research hub to supporting fundamental research in quantum science and £28M towards the creation of the Clyde Waterfront Innovation Campus, a new £80M development in collaboration with Glasgow City Council and Scottish Enterprise focussing on the translation of nano and quantum science for enabling technologies such as photonics, optoelectronics and quantum. Heriot-Watt has invested over £2M in new quantum optics laboratories and is currently building a £20M Global Research Innovation and Discovery Centre opening in 2019 to drive the translation of emerging technologies. Bristol is creating a £43M Quantum Innovation centre which already has £21M of industrial investment. Strathclyde University is creating a second £150M Technology Innovation Centre around 6 priority areas, one of which is Quantum Technology. All of these form part of the wider UK Quantum Technology Programme which is set to transform the UK's world leading science into commercial reality in line with the UK's drive towards a high productivity and high-skill economy. QuantIC will lead the quantum imaging research agenda and act as the bond between parallel activities and investments, thus ensuring paradigm-changing innovation that will transform tomorrow's society.

Single-photon counting - the ability to faithfully capture the single quantum of light - is a critical capability for a wide range of new low-light sensing applications and a host of emerging photonic quantum technologies. This proposed Programme Grant aims to significantly expand the operational region of single-photon detectors well beyond silicon's 1000nm wavelength limit into the short-wave infrared (SWIR) region of wavelengths between 1400nm to 3000nm, and part of the mid-wave infrared (MWIR) region between 3000nm and 5000nm. By scaling up SWIR and MWIR semiconductor and superconductor single-photon detectors to large area focal plane arrays, we will produce revolutionary new cameras with picosecond timing resolution which can be used, for example, to see though fog in automotive lidar scenarios, as well as allowing imaging and sensing in new applications in environmental monitoring, healthcare, and security and defence. The project will involve the design and fabrication of innovative new detector platforms of Ge-on-Si and III-V semiconductor detectors. The detectors are capable of single-photon sensitivity in the SWIR and MWIR regions, and will be fabricated in detector array format. We will also examine superconducting nanowires to expand their operation into the MWIR regions and fabricate arrayed detector configurations. A key part of the project is to integrate these arrayed detector technologies with read-out circuitry capable of rapid, low latency delivery of single-photon data. In addition, we will utilise micro-optic technology to optimise detection efficiency and demonstrate multiple wavelength filtering. The cameras will be designed for use in a range of applications areas, including lidar, where the time-of-flight of the return photons can be used for the measurement of distance. In arrayed detector format, we will make cameras from which we will demonstrate three-dimensional imaging at long distance, where the sensitivity and time-resolution will enhance imaging through dense fog and other obscurants. We will demonstrate our detector technologies in quantum cryptography applications, where encryption keys can be shared between two users. By sending data encoded in single-photons it is possible for the sender and receiver to share a secure, random key known only to them. The most critical component in this form of quantum communication is the single-photon detector - we will demonstrate the use of our detectors both in optical fibre and free-space quantum key distribution scenarios. Other emerging applications in spectroscopy and biophotonics will be demonstrated.