We aim to grow the world's leading centre for training in quantum engineering for the emerging quantum technology (QT) industry. We have designed this CDT in collaboration with a large number of academic and industry experts, and included as partners those who will add substantially to the training and cohort experience. Through this process a consistent picture of what industry wants in future quantum engineers emerged: people who can tackle the hardest intellectual challenges, recognising the end goal of their research, with an ability to move from fundamental physics towards the challenges of engineering and miniaturising practical systems, who understands the capabilities of other people (and why they are useful). Industry wants people with good decision-making, communication and management skills, with the ability to work across discipline boundaries (to a deadline and a budget!) and build interdisciplinary teams, with the ability to translate a problem from one domain to another. Relevant work experience, knowledge of entrepreneurship, industrial R&D operations and business practices are essential. By forming a hub of unrivalled international excellence in quantum information and photonics, surrounded by world-class expertise in all areas of underpinning science and technology and the scientific and technological application areas of QT, and a breadth of academic and industry partners, we will deliver a new type of training: quantum engineering. Bristol has exceptional international activity in the areas that surround the hub: from microelectronics and high performance computing to system engineering and quantum chemistry. The programme will be delivered in an innovative way-focussing particularly on cohort learning-and assessed by a variety of different means, some already in existence in Bristol. We believe that we are attempting something new and exciting that has the potential to attract and train the best students to ensure that the resulting capacity is world-class, thus providing real benefits to the UK economy.

Optical networks underpin the global digital communications infrastructure, and their development has simultaneously stimulated the growth in demand for data, and responded to this demand by unlocking the capacity of fibre-optic channels. The work within the UNLOC programme grant proved successful in understanding the fundamental limits in point-to-point nonlinear fibre channel capacity. However, the next-generation digital infrastructure needs more than raw capacity - it requires channel and flexible resource and capacity provision in combination with low latency, simplified and modular network architectures with maximum data throughput, and network resilience combined with overall network security. How to build such an intelligent and flexible network is a major problem of global importance. To cope with increasingly dynamic variations of delay-sensitive demands within the network and to enable the Internet of Skills, current optical networks overprovision capacity, resulting in both over- engineering and unutilised capacity. A key challenge is, therefore, to understand how to intelligently utilise the finite optical network resources to dynamically maximise performance, while also increasing robustness to future unknown requirements. The aim of TRANSNET is to address this challenge by creating an adaptive intelligent optical network that is able to dynamically provide capacity where and when it is needed - the backbone of the next-generation digital infrastructure. Our vision and ambition is to introduce intelligence into all levels of optical communication, cloud and data centre infrastructure and to develop optical transceivers that are optimally able to dynamically respond to varying application requirements of capacity, reach and delay. We envisage that machine learning (ML) will become ubiquitous in future optical networks, at all levels of design and operation, from digital coding, equalisation and impairment mitigation, through to monitoring, fault prediction and identification, and signal restoration, traffic pattern prediction and resource planning. TRANSNET will focus on the application of machine techniques to develop a new family of optical transceiver technologies, tailored to the needs of a new generation of self-x (x = configuring, monitoring, planning, learning, repairing and optimising) network architectures, capable of taking account of physical channel properties and high-level applications while optimising the use of resources. We will apply ML techniques to bring together the physical layer and the network; the nonlinearity of the fibres brings about a particularly complex challenge in the network context as it creates an interdependence between the signal quality of all transmitted wavelength channels. When optimising over tens of possible modulation formats, for hundreds of independent channels, over thousands of kilometres, a brute force optimisation becomes unfeasible. Particular challenges are the heterogeneity of large scale networks and the computational complexity of optimising network topology and resource allocation, as well as dynamical and data-driven management, monitoring and control of future networks, which requires a new way of thinking and tailored methodology. We propose to reduce the complexity of network design to allow self-learned network intelligence and adaptation through a combination of machine learning and probabilistic techniques. This will lead to the creation of computationally efficient approaches to deal with the complexity of the emerging nonlinear systems with memory and noise, for networks that operate dynamically on different time- and length-scales. This is a fundamentally new approach to optical network design and optimisation, requiring a cross-disciplinary approach to advance machine learning and heuristic algorithm design based on the understanding of nonlinear physics, signal processing and optical networking.

Pairing-based cryptography has boomed over the last decade since it provides secure solutions to problems where traditional cryptographic methods do not suffice or are less efficient. Boneh and Franklin in a seminal paper showed how to construct identity-based encryption using pairing-based techniques. This makes it possible to encrypt a message under somebody's identity, for instance their e-mail address, eliminating the need to obtain or manage a public key for each user. In large organizations this simplifies key management and identity-based key-management solutions are now used in several Fortune 500 companies. Another example arises in the context of pervasive computing systems such as intelligent cars that communicate with each other. In an intelligent car processing hundreds of messages from surrounding vehicles in every 300ms interval it is essential to minimize communication and optimise efficiency. Pairing-based digital signatures can be useful in this scenario because they are smaller than traditional digital signatures and at the same time allow for fast verification of a large batch of signatures at once. Other proposed applications of pairing-based cryptography include e-cash, searchable encrypted data, broadcast encryption and traitor tracing, delegatable anonymous credentials, and verifying the presence of data stored in a cloud computing facility. Security is essential in all of these tasks. As our society has become increasingly digitized and networked so have criminals, hackers, industrial spies, enemy states, etc. It is therefore necessary to design secure cryptographic schemes that can be used to build a digital society that is resilient in the presence of malicious adversaries. Designing cryptographic protocols for complex tasks requires significant effort and expertise since even a small mistake may render the entire system insecure. It is therefore natural to build cryptographic protocols in a modular fashion. This is what structure-preserving pairing-based cryptography allows. The term structure-preservation refers to pairing-based schemes that preserve their underlying mathematical structure. This structure-preserving property makes it easy to compose them with other pairing-based schemes and enables modular design. We will design structure-preserving pairing-based cryptographic schemes, study the efficiency limits of structure-preserving pairing-based cryptographic schemes and evaluate the security of pairing-based cryptographic schemes. By designing structure-preserving pairing-based schemes we develop new building blocks for the digital society. Moreover, the techniques we develop for the design of structure-preserving schemes may make it possible to build pairing-based schemes for significantly more complex tasks than is currently possible. Very recent work has shown that there are limits to how efficient structure-preserving digital signatures can be. It is usually very difficult to find efficiency limitations, researchers just tend to get stuck at some point without knowing why, but because of their unique nature structure-preserving protocols lend themselves to exact efficiency analysis. By finding efficiency limits for structure-preserving pairing-based schemes, we can get an accurate picture of the exact efficiency for a variety of cryptographic tasks. Security is essential when designing cryptographic protocols. The security of cryptographic schemes relies on hardness assumptions; for instance that it is computationally infeasible to factor large integers in a short amount of time. Unfortunately, pairing-based cryptographic schemes have been based on a large variety of assumptions making it hard to assess how secure they are. We will map out the landscape of assumptions that are used in pairing-based cryptography and make it easier to assess the security of pairing-based cryptographic schemes.

The description of the laws of quantum mechanics saw a transformation in society's understanding of the physical world-for the first time we understood the rules that govern the counterintuitive domain of the very small. Rather than being just passive observers now scientists are using these laws to their advantage and quantum phenomena are providing us with methods of improved measurement and communication; furthermore they promise a revolution in the way materials are simulated and computations are performed. Over the last decade significant progress has been made in the application of quantum phenomena to meeting these challenges. This "Engineering Photonic Quantum Technologies" Programme Grant goes significantly beyond previous achievements in the quantum technology field. Through a series of carefully orchestrated work packages that develop the underlying materials, systems engineering, and theory we will develop the knowledge and skills that enable us to create application demonstrators with significant academic and societal benefit. For the first time in quantum technologies we are combining materials and device development and experimental work with the important theoretical considerations of architectures and fault tolerant approaches. Our team of investigators and partners have the requisite expertise in materials, individual components, their integration, and the underpinning theory that dictates the optimal path to achieving the programme goals in the presence of real-world constraints. Through this programme we will adopt the materials systems most capable of providing application specific solutions in each of four technology demonstrations focused on quantum communications, quantum enhanced sensing, the construction of a multiplexed single-photon source and information processing systems that outperform modern classical analogues. To achieve this, our underlying technology packages will demonstrate very low optical-loss waveguides which will be used to create the necessary 'toolbox' of photonic components such as splitters, delays, filters and switches. We will integrate these devices with superconducting and semiconducting single-photon detector systems and heralded single-photon sources to create an integrated source+circuit+detector capability that becomes the basis for our technology demonstrations. We address the challenge of integrating these optical elements (in the necessary low-temperature environment) with the very low latency classical electronic control systems that are required of detection-and-feedforward schemes such as multiplexed photon-sources and cluster-state generation and computation. At all times a thorough analysis of the performance of all these elements informs our work on error modelling and fault tolerant designs; these then inform all aspects of the technology demonstrators from inception, through decisions on the optimal materials choices for a system, to the layout of a circuit on a wafer. With these capabilities we will usher in a disruptive transformation in ICT. We will demonstrate mutli-node quantum key distribution (QKD) networks, high-bit rate QKD systems with repeaters capable of spanning unlimited distances. Our quantum enhanced sensing will surpass the classical shot noise limit and see the demonstration of portable quantum-enhanced spectroscopy system. And our quantum information processors will operate with 10-qubits in a fault tolerant scheme which will provide the roadmap to 1,000 qubit cluster state computing architectures.

We are living through a revolution, as electronic communications become ever more ubiquitous in our daily lives. The use of mobile and smart phone technology is becoming increasingly universal, with applications beyond voice communications including access to social and business data, entertainment through live and more immersive video streaming and distributed processing and storage of information through high performance data centres and the cloud. All of this needs to be achieved with high levels of reliability, flexibility and at low cost, and solutions need to integrate developments in theoretical algorithms, optimization of software and ongoing advances in hardware performance. These trends will continue to shape our future. By 2020 it is predicted that the number of network-connected devices will reach 1000 times the world's population: there will be 7 trillion connected devices for 7 billion people. This will result in 1.3 zettabytes of global internet traffic by 2016 (with over 80% of this being due to video), requiring a 27% increase in energy consumption by telecommunications networks. The UK's excellence in communications has been a focal point for inward investment for many years - already this sector has a value of £82Bn a year to the UK economy (~5.7% GDP). However this strength is threatened by an age imbalance in the workforce and a shortage of highly skilled researchers. Our CDT will bridge this skills gap, by training the next generation of researchers, who can ensure that the UK remains at the heart of the worldwide communications industry, providing a much needed growth dividend for our economy. It will be guided by the commercial imperatives from our industry partners, and motivated by application drivers in future cities, transport, e-health, homeland security and entertainment. The expansion of the UK internet business is fuelled by innovative product development in optical transport mechanisms, wireless enabled technologies and efficient data representations. It is thus essential that communications practitioners of the future have an overall system perspective, bridging the gaps between hardware and software, wireless and wired communications, and application drivers and network constraints. While communications technology is the enabler, it is humans that are the producers, consumers and beneficiaries in terms of its broader applications. Our programme will thus focus on the challenges within and the interactions between the key domains of People, Power and Performance. Over three cohorts, the new CDT will build on Bristol's core expertise in Efficient Systems and Enabling Technologies to engineer novel solutions, offering enhanced performance, lower cost and reduced environmental impact. We will train our students in the mathematical fundamentals which underpin modern communication systems and deliver both human and technological solutions for the communication systems landscape of the future. In summary, Future Communications 2 will produce a new type of PhD graduate: one who is intellectually leading, creative, mathematically rigorous and who understands the commercial implications of his or her work - people who are the future technical leaders in the sector.