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 the next generation devices, whose performances will beat those of classical machines. Quantum sensors, in particular, exploit the intrinsic "weakness" of quantum systems, their extreme sensitivity to external perturbations, to provide measurements of the perturbing fields with unprecedented sensitivity and stability. This project targets the realization of ultra-sensitive quantum magnetometers based on neutral atoms at room temperature, for studying the brain function by accessing its connectivity. Detection of very small magnetic fields of biological origin allows a non-invasive study of the spatial and time dependence of bio-currents. Therefore, a logical and very promising direction of application of non-invasive ultra-sensitive quantum magnetometers is the realization of probes for measuring the magnetic fields generated by the neuronal activity of the human brain. Recent technological developments have made it possible to employ atomic magnetometers (AMs) in the context of magnetoencephalography (MEG) analysis. Here we propose to further develop AMs-based MEG for accessing information on the brain connectivity, by combining these quantum sensors with the technique of transcranial brain stimulation (TMS). Indeed, the nerve cells of the brain can be inductively stimulated by applying a short but strong magnetic pulse localized at a specific region of the brain. Causal brain connectivity will be directly studied by measuring the magnetic response of different brain areas to this stimulus. The aim is to estimate the directional coupling and the temporal interaction of different brain sectors, which requires sensors with large sensitivity, real-time operation, and adequate spatial resolution. The core of this project is the realization of all-optical AMs compatible with TBS. The key point is that the sensors need to rapidly recover following a relatively strong magnetic stimulation, to record the brain signals no more than few tens ms after the pulse. The integration of AM sensors and TMS coil will be done in few steps, with the goal of both minimizing the effects induced by the TMS coil and shortening the sensor dead-time. The sensor will be then prepared for operation in a medical environment. In parallel, we will boost the miniaturization of the AMs, which is necessary for achieving a millimetre-spatial resolution and a dense package of the sensors over the head, and its measurement bandwidth. Miniaturization usually comes at the price of an important loss of sensitivity. To improve magnetic sensitivity in highly miniaturized sensors, we will prepare and use a class of entangled atomic states known as spin-squeezed states. We propose a novel, simple and robust way to achieve spin-squeezing, which has the potential to largely surpass state-of-the-art techniques in atomic magnetometry. Within this project, we expect to implement ultra-sensitive highly miniaturized AMs as innovative tools to directly measure human brain connectivity, for understanding healthy brain functionality, as well as for clinical diagnostics and treatment of brain injuries and neurological disorders.

The core aim of this proposal is to implement a novel technique to assess the connectivity in the human brain by developing optically pumped magnetometers (OPMs) that can be combined with transcranial magnetic stimulation (TMS). This allows us to assess brain connectivity by stimulating one region and measuring the response in another region. The approach holds the promise of providing capabilities needed for understanding the brain as a network and to investigate brain connectivity in cognition and disorders. Currently there is strong enthusiasm for OPMs. This new type of sensor has the potential of revolutionizing human electrophysiology. In particular OPMs allow us to measure small magnetic fields from neuronal currents in the brain, which so far is usually done using conventional SQUID-based magnetoencephalography (MEG). The disadvantages of conventional MEG are that 1) the sensors rely on cooling by liquid Helium which is highly expensive and 2) the sensors cannot work with brain stimulation. OPMs solve both concerns but need to be further developed to be integrated with brain stimulation. Brain stimulation using TMS is used to activate a given brain region by delivering a brief but strong magnetic pulse. The technique can also be used to stimulate one brain region and measure the response in connected regions. This has recently been attempted by combining TMS with electroencephalography (EEG); however, the resulting signals are spatially blurred and therefore difficult to interpret. Combining TMS with OPMs holds the promise of better identifying the regions responding to a specific perturbation. As such it will allow us to measure connectivity in the brain and quantify how this connectivity is modulated in a task specific manner. Furthermore, the technique can be used to assess connectivity changes associated with brain injuries and neurological disorders. Specifically, we will develop a new type of OPMs that can be used together with TMS. These new sensors will be benchmarked against conventional MEG sensors. Subsequently we will test the OPMs together with TMS. This will first be done using phantom recordings and subsequently tested in humans performing various tasks hypothesized to modulate brain connectivity. Within this proposal we are aiming at using up to 5 sensors. Therefore, B-conn will provide the stepping-stone for developing a whole-head OPM-MEG system with ~100 sensors in collaboration with commercial and academic partners. The longer-term goal is to develop an integrated stimulus-response system that can be used in clinical settings for diagnostic purposes by quantifying alterations in brain connectivity associated with communication delays and strengths. Examples are traumatic brain injury and neurodegenerative diseases.

Topology is a particular study of the spatial structure of objects, based on counting discrete properties, such as the number of holes and bridges in a sponge. Whichever way the sponge is stretched or squeezed, these numbers stay the same. In fact, the elastic properties of the sponge depend on this structure. It turns out that topological properties like this play a role in the physical properties of certain materials, such as the way they conduct electricity or how light propagates through them. This has led to an explosion of research and development into new kinds of materials with unprecedented properties, designed using fundamental physical and mathematical principles which can be fabricated and, in the future, manufactured on a large scale. We will train the first cohort of doctoral topological scientists, who will have a broad expertise in topological science and design, focused towards the development of new topological materials that address the needs of industry. Drawn from mathematically-informed backgrounds including physics, engineering and materials science, they will develop a broad technical appreciation of topological design within all of these disciplines, and gain research experience in mini-projects in theoretical and experimental groups. Their main PhD research project can be with supervisors drawn from all academic Schools in the College of Engineering and Physical Sciences at the University of Birmingham, in partnership with our wide range of partners from industry. This technical education will be entwined with a programme of transferable skills developing the critical skills of innovation, entrepreneurship and responsible innovation. The academic leadership of this CDT has co-created the training programme in collaboration with a range of industrial partners who will contribute to the directions of the research projects, provide internships and help the students and academic supervisors focus on the needs of end users in their research. These partners will not only be drawn from relevant industries, such as communications, manufacturing and defence sectors, but more widely from knowledge industries including software developers and commercialisation lawyers. The resulting CDT will be a beacon for cross-disciplinary research across the physical sciences and spearheading academic-industrial partnership over the coming decades as topological design becomes a crucial principle for the development of future technologies, underpinning the future prosperity of the UK.

The Quantum Technology Hub in Sensors and Timing, a collaboration between 7 universities, NPL, BGS and industry, will bring disruptive new capability to real world applications with high economic and societal impact to the UK. The unique properties of QT sensors will enable radical innovations in Geophysics, Health Care, Timing Applications and Navigation. Our established industry partnerships bring a focus to our research work that enable sensors to be customised to the needs of each application. The total long term economic impact could amount to ~10% of GDP. Gravity sensors can see beneath the surface of the ground to identify buried structures that result in enormous cost to construction projects ranging from rail infrastructure, or sink holes, to brownfield site developments. Similarly they can identify oil resources and magma flows. To be of practical value, gravity sensors must be able to make rapid measurements in challenging environments. Operation from airborne platforms, such as drones, will greatly reduce the cost of deployment and bring inaccessible locations within reach. Mapping brain activity in patients with dementia or schizophrenia, particularly when they are able to move around and perform tasks which stimulate brain function, will help early diagnosis and speed the development of new treatments. Existing brain imaging systems are large and unwieldy; it is particularly difficult to use them with children where a better understanding of epilepsy or brain injury would be of enormous benefit. The systems we will develop will be used initially for patients moving freely in shielded rooms but will eventually be capable of operation in less specialised environments. A new generation of QT based magnetometers, manufactured in the UK, will enable these advances. Precision timing is essential to many systems that we take for granted, including communications and radar. Ultra-precise oscillators, in a field deployable package, will enable radar systems to identify small slow-moving targets such as drones which are currently difficult to detect, bringing greater safety to airports and other sensitive locations. Our world is highly dependent on precise navigation. Although originally developed for defence, our civil infrastructure is critically reliant on GNSS. The ability to fix one's location underground, underwater, inside buildings or when satellite signals are deliberately disrupted can be greatly enhanced using QT sensing. Making Inertial Navigation Systems more robust and using novel techniques such as gravity map matching will alleviate many of these problems. In order to achieve all this, we will drive advanced physics research aimed at small, low power operation and translate it into engineered packages to bring systems of unparalleled capability within the reach of practical applications. Applied research will bring out their ability to deliver huge societal and economic benefit. By continuing to work with a cohort of industry partners, we will help establish a complete ecosystem for QT exploitation, with global reach but firmly rooted in the UK. These goals can only be met by combining the expertise of scientists and engineers across a broad spectrum of capability. The ability to engineer devices that can be deployed in challenging environments requires contributions from physics electronic engineering and materials science. The design of systems that possess the necessary characteristics for specific applications requires understanding from civil and electronic engineering, neuroscience and a wide range of stakeholders in the supply chain. The outputs from a sensor is of little value without the ability to translate raw data into actionable information: data analysis and AI skills are needed here. The research activities of the hub are designed to connect and develop these skills in a coordinated fashion such that the impact on our economy is accelerated.