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.

Quantum technologies (QT) are new, disruptive information technologies that can outperform their conventional counterparts, in communications, sensing, imaging and computing. The UK has already invested significantly in a national programme for QT, to develop and exploit these technologies, and is now investing further to stimulate new UK industry and generate a supply of appropriately skilled technologists across the range of QT sectors. All QT exploit the various quantum properties of light or matter in some way. Our work is in the communications sector, and is based on the fundamental effect that measuring or detecting quantum light signals irreversibly disturbs them. This effect is built into Nature, and will not go away even when technologies (quantum or conventional) are improved in the future. The fundamental disturbance of transmitted quantum light signals enables secure communications, as folk intercepting signals when they are not supposed to (so-called eavesdroppers) will always get caught. This means Alice and Bob can use quantum light signals to set up secure shared data, or keys, which they can then use for a range of secure communications and transactions - this is quantum key distribution (QKD). The irreversible disturbance of light can also be used to generate random numbers - another very important ingredient for secure communications, cryptology, simulation and modelling. In the modern world where communications are so ubiquitous and important, there is increasing demand for new secure methods. Technologies and methods widely used today will be vulnerable to emergent quantum computing technologies, so encrypted information being sent around today which has a long security shelf-life will be at risk in the future. New "quantum safe" methods that are not vulnerable to any future QT have to be developed. So QKD and new mathematical encryption must be made practical and cost effective, and soon. The grand vision of the Quantum Communications Hub is therefore to pursue quantum communications at all distance scales, to offer a range of applications and services and the potential for integration with existing infrastructure. Very short distance communications require free space connections for flexibility. Examples include between a phone or other handheld device and a terminal, or between numerous devices and a fixed receiver in a room. The Hub will be engineering these "many-to-one" technologies to enhance practicality and real-world operation. Longer distance conventional communications - at city, metropolitan and inter-city scales - already use optical fibres, and quantum communications have to leverage and complement this. The Hub has already established the UK's first quantum network, the UKQN. We will be extending and enhancing the UKQN, adding function and capability, and introducing new QKD technologies - using quantum light analogous to that used in conventional communications, or using entanglement working towards even longer distance fibre communications. The very longest distance communications - intercontinental and across oceans - require satellites. The Hub will therefore work on a new programme developing ground to satellite QKD links. Commercial QKD technologies for all distance scales will require miniaturisation, for size, weight and power savings, and to enable mass manufacture. The Hub will therefore address key engineering for on-chip operation and integration. Although widely applicable, key-sharing does not provide a solution for all secure communication scenarios. The Hub will therefore research other new quantum protocols, and the incorporation of QKD into wider security solutions. Given the changing landscape worldwide, it is becoming increasingly important for the UK to establish national capability, both in quantum communication technologies and their key components such as light sources and detectors. The Hub has assembled an excellent team to deliver this capability.

Photonics is one of the largest and fasted growing markets of the world economy. Optical technologies are key to a vast range of applications from telecommunications networks to sensor and metrology equipment and are being actively developed by industrial giants such as IBM, Intel and Cisco. In a similar way to the evolution experienced by electronics, the demand for photonics devices with smaller footprint, lower cost and higher functionality has propelled the rapid development of integrated "photonics chips". Thanks to the legacy provided by decades of enormous investments in the electronic industry, silicon is rapidly becoming the standard material platform for photonic integrated chips. However, because of its crystalline structure, silicon is a very poor light emitter and, therefore, truly integrated devices that can emit, process and detect light on-chip still represent a major challenge. III-V semiconductor materials such as InP or GaAs provide far better performance in terms of light emission but cannot compete with silicon in terms of large volume manufacturing and cost. Combining the "best from the two worlds", i.e. heterogeneously integrating III-V light emitters on a silicon material platform, is regarded as a promising solution to circumvent the deficiencies of silicon yet keeping compatibility with industrial silicon manufacturing paradigms to allow scaling to wafer level complex products without requiring a full retooling of the supply chain. Building on established expertise in photonic integrated devices and transfer printing technologies at Glasgow and Strathclyde universities, this proposal will develop an assembly technique to integrate active III-V membrane devices onto passive silicon photonic integrated circuits. The method will demonstrate parallel transfer of multiple devices with sub-micrometer positional accuracy and scalability to wafer-level production. The developed techniques will exploit fully back-end processes, making them compatible with current foundry standards and therefore commercial interests. Key demonstrators in optical communications, gas sensing and high density data storage will be developed to illustrate the flexibility of the methods and potential across a wide range of application spaces. The project will benefit from the support from several academic and industrial partners who will provide resources and expertise in key areas such as wafer-scale manufacturing of III-V optical devices (CST), transfer printing system engineering (Fraunhofer), optical transceivers for telecomm and datacentre markets (Huawei), micro-assembly of active/passive photonic systems (Kaiam), integrated photonic devices for HDD data storage (Seagate), mid-IR gas sensors (GSS), large-scale silicon photonics devices (Southampton University). The proposal aligns with EPSRC's Manufacturing the Future theme and the Photonics for Future Systems priority, and addresses specific portfolio areas such as Manufacturing Technologies, Optical Communications, Optical Devices & Subsystems, Optoelectronic Devices & Circuits, Components & Systems

Quantum computing, once a purely theoretical dream, is becoming a reality. The last two years - 2019 and 2020 - have seen the first demonstrations of quantum advantage, that is, quantum computers performing tasks that cannot be solved by any classical supercomputer in a reasonable time. Among the competing technologies, photonics and superconducting circuits are the only two that reached quantum advantage. In both cases, the challenge ahead is scalability: the current quantum machines can only process a limited number of quantum bits, limiting their application to the solution of proof-of-concept problems. This project aims to develop a highly complex quantum state, called cluster state, that underpins a scalable approach to photonic quantum computing. Such a state, to be useful, must live on miniaturised components fabricated by a mature technology that supports scalability with increased complexity and commercial viability. Integrated photonics satisfies both these requirements. It can count on a large selection of tools and devices developed during the last forty years for telecommunications and data processing and employs the latest technologies that connect classical computers. This project will use the latest discoveries and technologies of integrated photonics for realising the generation of the aforementioned cluster states on-chip. One of the more recent and striking successes of integrated photonics is the realisation of frequency combs on-chip (microcombs). Frequency combs, electromagnetic fields composed by many equidistant frequencies (light colours), are a powerful resource for metrology and spectroscopy. Their miniaturisation via integrated photonics transformed them from cumbersome bulk systems to few millimetres squared chips, making integrated frequency combs one of the most promising photonic technologies. Frequency combs feature thousands to millions of modes and land themselves naturally to host the cluster states required for scalable quantum computation. To transform an integrated frequency comb into a cluster state all its frequency modes must be entangled, that is, sharing the same quantum state. Here, I propose a research programme that tackles this very problem: generating an integrated cluster state based on frequency combs. The research developed in this proposal will disclose the potential of integrated quantum frequency combs for quantum computing. This will boost a number of applications identified as strategic by the UK Government and Research Councils such as clock synchronisation and the deployment of quantum technologies.

This Hub accelerates progress towards a new "quantum era" by engineering small, high precision quantum systems, and linking them into a network to create the world's first truly scalable quantum computing engine. This new computing platform will harness quantum effects to achieve tasks that are currently impossible. The Hub is an Oxford-led alliance of nine universities with complementary expertise in quantum technologies including Bath, Cambridge, Edinburgh, Leeds, Strathclyde, Southampton, Sussex and Warwick. We have assembled a network of more than 25 companies (Lockheed-Martin, Raytheon BBN, Google, AMEX), government labs (NPL, DSTL, NIST) and SMEs (PureLiFi, Rohde & Schwarz, Aspen) who are investing resources and manpower. Our ambitious flagship goal is the Q20:20 engine - a network of twenty optically-linked ion-trap processors each containing twenty quantum bits (qubits). This 400 qubit machine will be vastly more powerful than anything that has been achieved to date, but recent progress on three fronts makes it a feasible goal. First, Oxford researchers recently discovered a way to build a quantum computer from precisely-controlled qubits linked with low precision by photons (particles of light). Second, Oxford's ion-trap researchers recently achieved a new world record for precision qubit control with 99.9999% accuracy. Third, we recently showed how to control photonic interference inside small silica chips. We now have an exciting opportunity to combine these advances to create a light-matter hybrid network computer that gets the 'best of both worlds' and overcomes long-standing impracticalities like the ever increasing complexity of matter-only systems, or the immense resource requirements of purely photonic approaches. Engineers and scientists with the hub will work with other hubs and partners from across the globe to achieve this. At present proof-of-principle experiments exist in the lab, and the 'grand challenge' is to develop compact manufacturable devices and components to build the Q20:20 engine (and to make it easy to build more). We have already identified more than 20 spin-offs from this work, ranging from hacker-proof communication systems and ultra-sensitive medical and military sensors to higher resolution imaging systems. Quantum ICT will bring great economic benefits and offer technical solutions to as yet unsolveable problems. Just as today's computers allow jet designers to test the aerodynamics of planes before they are built, a quantum computer will model the properties of materials before they've been made, or design a vital drug without the trial and error process. This is called digital quantum simulation. In fact many problems that are difficult using conventional computing can be enhanced with a 'quantum co-processor'. This is a hugely desirable capability, important across multiple areas of science and technology, so much so that even the prospect of limited quantum capabilities (e.g. D-Wave's device) has raised great excitement. The Q20:20 will be an early form of a verifiable quantum computer, the uncompromised universal machine that can ultimately perform any algorithm and scale to any size; the markets and impacts will be correspondingly far greater. In addition to computing there will be uses in secure communications, so that a 'trusted' internet becomes feasible, in sensing - so that we can measure to new levels of precision, and in new components - for instance new detectors that allow us to collect single photons. The hub will ultimately become a focus for an emerging quantum ICT industry, with trained scientists and engineers available to address the problems in industry and the wider world where quantum techniques will be bringing benefits. It will help form new companies, new markets, and grow the UK's knowledge economy.