Quantum dots (QDs) are nanoscale regions of semiconductor, embedded within a much larger host of a second semiconductor. The differing properties of the two semiconductors mean that single particles of charge (electrons) can be trapped within a QD, allowing for study of light-matter interactions on a single particle level. In particular, QDs form an excellent source of the quantum states of light (photons) that are required for many exciting new quantum technologies such as secure communication and enhanced sensing. A consequence of the solid-state host is that the QD interacts with its local environment, a particularly important example being quantised vibrations of the lattice, termed phonons. These interactions have typically been considered an unwelcome but unavoidable consequence of working with QDs and other similar solid-state systems. This proposal aims to demonstrate that through appropriate nano-fabrication and control of the QD geometry, the interaction of the QD with both its optical (photonic) and vibrational (phononic) environments can be controlled. By realising such control over environmental interactions, the impact of phonon interactions on the photons emitted can be almost eliminated, increasing the efficiency and quality of the QD photon source to support new applications. Furthermore, the need for extreme cryogenic cooling can be greatly reduced, removing a significant barrier to quantum technologies applications. Harnessing these developments, several novel quantum technologies will be developed based on the QD platform. Quantum 2-photon microscopy offers the potential to perform imaging of delicate samples that would be damaged by the intense light fields required for current methods. Meanwhile, high sensitivity optical sensing can be realised by using phonon interactions to "squeeze" the uncertainty in photons emitted by the QD. Finally, quantum data locking offers the potential for quantum-secured communication with a significantly higher efficiency than existing methods.

Light emitting semiconductor materials and devices dominate many aspects of everyday life. Their influence is all pervasive providing the sources which enable the internet, large area displays, room and street lighting to give just a few examples. Their existence relies on the high quality semiconductor structures which may be prepared by advanced crystal growth and sophisticated nanofabrication. Our proposal aims to capitalise on the advanced growth and fabrication to achieve similar advances in the quantum world where often counter-intuitive behaviour is governed solely by the laws of quantum mechanics. Our overall aim is to explore the behaviour of nano-devices operating in regimes where fundamentally new types of quantum-photonic phenomena occur, with potential to underpin the next generation of quantum technologies. We focus on two complementary systems: III-V semiconductors with their highly perfect crystal lattices, proven ability to emit photons one by one and long coherence quantum states, and atomically-thin graphene-like two dimensional (2D) semiconductors enabling new band structures, stable electron-hole bound states (excitons) and easy integration with patterned structures. The combination of the two material systems is powerful enabling phenomena ranging from the single photon level up to dense many-particle states where interactions dominate. A significant part of our programme focusses on on-chip geometries, enabling scale-up as likely required for applications. The semiconductor systems we employ interact strongly with photons; we will achieve interactions between photons which normally do not interact. We will gain entry into the regime of highly non-linear cavity quantum electrodynamics. Excitons (coupled electron-hole pairs) and photons interact strongly, enabling ladders of energy levels leading to on-chip production of few photon states. By coupling cavities together, we will aim for highly correlated states of photons. These advances are likely to be important components of photonic quantum processors and quantum communication systems. In similar structures, we access regimes of high density where electrons and holes condense into highly populated states (condensates). We aim to answer long-standing fundamental questions about the types of phase transitions that can occur in equilibrium systems and in out-of-equilibrium ones which have loss balanced by gain. We will also study condensate systems up to high temperatures, potentially in excess of 100K, and of the mechanisms underlying phase transitions to condensed states. The condensed state systems, besides their fundamental interest, also have potential as new forms of miniature coherent light sources. Nanofabrication will play a vital role enabling confinement of light on sub-wavelength length scales and fabrication of cavities for photons such that they have very long lifetimes before escaping. The ability to place high quality emitters within III-V nanophotonic structures will receive enhancement and potential world lead from a crystal growth machine we have recently commissioned, specially designed for this purpose, funded by the UK Quantum Technologies programme. Similar impact is expected from our ability to prepare 2D heterostructures (atomically thin layers of two separate materials placed one on top of the other) under conditions of ultrahigh vacuum free from contamination, enabling realisation of bound electron-hole pair states of very long lifetime, the route to condensation to high density states. The easy integration of 2D heterostructures with patterned photonic structures furthermore enables nonlinear and quantum phenomena to be studied, including in topological structures where light flow is immune to scattering by defects. Taken all together we have the ingredients in place to achieve ground-breaking advances in fundamental quantum photonics with considerable potential to underpin next generations of quantum technologies.

Quantum Technology is based on quantum phenomena that govern physics on an atomic scale, enabling key breakthroughs that enhance the performance of classical devices and allow for entirely new applications in communications technology, imaging and sensing, and computation. Quantum networks will provide secure communication on a global scale, quantum sensors will revolutionise measurements in fields such as geology and biomedical imaging, and quantum computers will efficiently solve problems that are intractable even on the best future supercomputers. The economic and societal benefit will be decisive, impacting a wide range of industries and markets, including engineering, medicine, finance, defence, aerospace, energy and transport. Consequently, Quantum Technologies are being prioritised worldwide through large-scale national or trans-national initiatives, and a healthy national industrial Quantum Technology ecosystem has emerged including supply chain, business start-ups, and commercial end users. Our Centre for Doctoral Training in Applied Quantum Technologies (CDT-AQT) will address the national need to train cohorts of future quantum scientists and engineers for this emerging industry. The training program is a partnership between the Universities of Strathclyde, Glasgow and Heriot-Watt. In collaboration with more than 30 UK industry partners, CDT-AQT will offer advanced training in broad aspects of Quantum Technology, from technical underpinnings to applications in the three key areas of Quantum Measurement and Sensing, Quantum Computing and Simulation, and Quantum Communications. Our programme is designed to create a diverse community of responsible future leaders who will tackle scientific and engineering challenges in the emerging industrial landscape, bring innovative ideas to market, and work towards securing the UK's competitiveness in one of the most advanced and promising areas of the high-tech industry. The quality of our training provision is ensured by our supervisors' world-class research backgrounds, well-resourced research environments at the host institutions, and access to national strategic facilities. Industry engagement in co-creation and co-supervision is seen as crucial in equipping our students with the transferable skills needed to translate fundamental quantum physics into practical quantum technologies for research, industry, and society. To benefit the wider community immediately, we will make Quantum Technologies accessible to the general public through dedicated outreach activities, in which our students will showcase their research and exhibit at University Open Days, schools, science centres and science festivals.

Quantum technology will revolutionise many aspects of life and bring enormous benefits to the economy and society. The Centre for Doctoral Training in Quantum Informatics (QI CDT) will provide advanced training in the structure, behaviour, and interaction of quantum hardware, software, and applications. The training programme spans computer sciences, mathematics, physics, and engineering, and will enable the use of quantum technology in a way that is integrable, interoperable, and impactful, rather than developing the hardware itself. The training programme targets three research challenges with a strong focus on end user impact: (i) quantum service architecture concerns how to design quantum networks and devices most usefully; (ii) scalable quantum software is about feasible application at scale of quantum technology and its integration with other software; and (iii) quantum application analysis investigates how quantum technology can be used most advantageously to solve end user problems. The QI CDT will offer 75+ PhD students an intensive 4-year training and research programme that equips them with the skills needed to tackle the research challenges of quantum informatics. This new generation will be able to integrate quantum hardware with high-performance computing, design effective quantum software, and apply this in a societally meaningful way. The QI CDT brings together a coalition with national reach including over 65 academic experts in quantum informatics from five universities - the University of Edinburgh, the University of Oxford, University College London, Heriot-Watt University, and the University of Strathclyde - and three public sector partners - the National Quantum Computing Centre, the National Physical Laboratory, and the Hartree Centre. A network of over 30 industry partners, diverse in size and domain expertise, and 9 leading international universities, give students the best basis for meaningful and collaborative research. A strong focus on cohort-based training will make QI CDT students into a diverse network of future leaders in Quantum Informatics in the UK.

o achieve this vision, we will address major global research challenges towards the establishment of the "quantum internet" —?globally interlinked quantum networks which connect quantum nodes via quantum channels co-existing with classical telecom networks. These research challenges include: low-noise quantum memories with long storage time; connecting quantum processors at all distance scales; long-haul and high-rate quantum communication links; large-scale entanglement networks with agile routing capabilities compatible with - and embedded in - classical telecommunicatons networks; cost-effective scalability, standardisation, verification and certification. By delivering technologies and techniques to our industrial innovation partners, the IQN Hub will enable UK academia, national laboratories, industry, and end-users to be at the forefront of the quantum networking revolution. The Hub will utilise experience in the use of photonic entanglement for quantum key distribution (QKD) alongside state-of-the art quantum memory research from existing EPSRC Quantum Technology Hubs and other projects to form a formidable consortium tackling the identified challenges. We will research critical component technology, which will underpin the future national supply chain, and we will make steps towards global QKD and the intercontinental distribution of entanglement via satellites. This will utilise the Hub Network's in-orbit demonstrator due to be launched in late 2024, as well as collaboration with upcoming international missions. With the National Quantum Computing Centre (NQCC), we will explore applications towards quantum advantage demonstrations such as secure access to the quantum cloud, achievable only through entanglement networks. Hub partner National Physical Laboratory (NPL) working with our academic partners and the National Cyber Security Centre (NCSC) will ensure that our efforts are compatible with emerging quantum regulatory standards and post-quantum cybersecurity to bolster national security. We will foster synergies with competing international efforts through healthy exchange with our global partners. The Hub's strong industrial partner base will facilitate knowledge exchange and new venture creation. Achieving the IQN Hub's vision will provide a secure distributed and entanglement-enabled quantum communication infrastructure for UK end-users. Industry, government stakeholders and the public will be able to secure data in transit, in storage and in computation, exploiting unique quantum resources and functionalities. We will use a hybrid approach with existing classical cyber-security standards, including novel emerging post-quantum algorithms as well as hardware security modules. We will showcase our ambition with target use-cases that have emerged as barriers for industry, after years of investigation within the current EPSRC QT Hubs as well as other international efforts. These barriers include security and integrity of: (1) device authentication, identification, attestation, verification; (2) distributed and cloud computing; (3) detection, measurement, sensing, synchronisation. We will demonstrate novel applications as well as identify novel figures of merit (such as resilience, accuracy, sustainability, communication complexity, cost, integrity, etc.) beyond security enhancement alone to ensure the national quantum entanglement network can be fully exploited by our stakeholders and our technology can be rapidly translated into a commercial setting.