The advent of practical quantum computers, expected within the next two decades, poses a serious threat to most of standard encryption systems. Quantum Key Distribution (QKD) and Quantum Random Number Generators (QRNGs) aim to enhance security of communications and personal data by exploiting the laws of Quantum Mechanics and provide the solution to threat caused by a malicious use of quantum computers. QRNGs, exploiting the probabilistic nature of quantum measurements, produce truly random numbers. This is in opposition with current methods to generate random numbers which combine the use of chaotic systems and software-based pseudo random number generators. QKD systems taking advantage specific features of quantum systems such as superposition of quantum states and the "no-cloning" theorem enable parties to exchange cryptographic keys in an intrinsically secure way. Because QKD key exchange is based on physical systems as opposed to software-based encryption methods, QKD is also "future-proof" as no improvement on hacking algorithm will affect the security of the protocols. In the last few years, the efforts of the QKD and QRNG community have focused first to produce lab prototypes and more recently to provide commercial systems, which have been deployed in small scale around the globe. However, less focus has been placed on key aspects such as the form factor and technology scalability as well as power consumption and costs. Systems built with optical fibres and discrete electronics components are inevitably expensive, bulky, and limited in terms of performance and therefore intrinsically not scalable. KETS Quantum Security Ltd, spin-off of the Quantum Engineering Technology Labs (University of Bristol) has been addressing the scalability issues by combining the advantages of integrated photonics technologies and quantum cryptography protocols. While the integrated photonic chips have significantly reduced the size of the core optical system, separation between discrete electronic components and photonic chips inherently limits the overall performance of the quantum technology. Moreover, this increases the size of the devices and their costs, limiting the spread of this QKD and QRNG systems. The focus of this fellowship would be the development of some novel critical integrated opto-electronics systems, where microelectronics and quantum photonics will be monolithically integrated on the same semiconductor substrate. Monolithic integration of electronics and photonics is a critical technological step forward that will open the way to a whole new range of solutions and will improve the performance of quantum technologies potentially by orders of magnitude. This could bring groundbreaking improvements to QKD and QRNG systems, opening the way to their direct integration onto modern digital technologies.

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.

Quantum Technologies (QT) are at a pivotal moment with major global efforts underway to translate quantum information science into new products that promise disruptive impact across a wide variety of sectors from communications, imaging, sensing, metrology, simulation, to computation and security. Our world-leading Centre for Doctoral Training in Quantum Engineering will evolve to be a vital component of a thriving quantum UK ecosystem, training not just highly-skilled employees, but the CEOs and CTOs of the future QT companies that will define the field. Due to the excellence of its basic science, and through investment by the national QT programme, the UK has positioned itself at the forefront of global developments. There have been very recent major [billion-dollar] investments world-wide, notably in the US, China and Europe, both from government and leading technology companies. There has also been an explosion in the number of start-up companies in the area, both in the UK and internationally. Thus, competition in this field has increased dramatically. PhD trained experts are being recruited aggressively, by both large and small firms, signalling a rapidly growing need. The supply of globally competitive talent is perhaps the biggest challenge for the UK in maintaining its leading position in QT. The new CDT will address this challenge by providing a vital source of highly-trained scientists, engineers and innovators, thus making it possible to anchor an outstanding QT sector here, and therefore ensure that UK QT delivers long-term economic and societal benefits. Recognizing the nature of the skills need is vital: QT opportunities will be at the doctoral or postdoctoral level, largely in start-ups or small interdisciplinary teams in larger organizations. With our partners we have identified the key skills our graduates need, in addition to core technical skills: interdisciplinary teamwork, leadership in large and small groups, collaborative research, an entrepreneurial mind-set, agility of thought across diverse disciplines, and management of complex projects, including systems engineering. These factors show that a new type of graduate training is needed, far from the standard PhD model. A cohort-based approach is essential. In addition to lectures, there will be seminars, labs, research and peer-to-peer learning. There will be interdisciplinary and grand challenge team projects, co-created and co-delivered with industry partners, developing a variety of important team skills. Innovation, leadership and entrepreneurship activities will be embedded from day one. At all times, our programme will maximize the benefits of a cohort-based approach. In the past two years particularly, the QT landscape has transformed, and our proposed programme, with inputs from our partners, has been designed to reflect this. Our training and research programme has evolved and broadened from our highly successful current CDT to include the challenging interplay of noisy quantum hardware and new quantum software, applied to all three QT priorities: communications; computing & simulation; and sensing, imaging & metrology. Our programme will be founded on Bristol's outstanding activity in quantum information, computation and photonics, together with world-class expertise in science and engineering in areas surrounding this core. In addition, our programme will benefit from close links to Bristol's unique local innovation environment including the visionary Quantum Technology Enterprise Centre, a fellowship programme and Skills Hub run in partnership with Cranfield University's Bettany Centre in the School of Management, as well as internationally recognised incubators/accelerators SetSquared, EngineShed, UnitDX and the recently announced £43m Quantum Technology Innovation Centre. This will all be linked within Bristol's planned £300m Temple Quarter Enterprise Campus, placing the CDT at the centre of a thriving quantum ecosystem.