The coming revolution in quantum computing technologies creates some exciting challenges for engineers and equally exciting business opportunities for existing companies and new start-ups. One of these challenges is that existing superconducting quantum computers are already overcrowded with dense wiring and bulky microwave components, there is simply limited physical space in the dilution refrigerators. Moving to the 100-1000-qubit level and beyond requires new solutions for scalable and cost-effective microwave control and measurement circuity. Simply put, the microwave control systems need to be of much lighter weight and smaller physical size than at present with a high level of integration while being cost-effective and energy efficient. Some of the critically required cryogenic microwave control components are dense wiring, attenuators, and circulators, which are used to bring control signals from the electronics into the cryostat, to allow the transmission of desired frequency bands while rejecting unwanted bands and to protect quantum processors against reflected signals and decoherence. Typically, dense wiring connections, filters and circulators occupy quite a large size in the cryostat and the number of them needed is growing rapidly as we scale up the number of qubits. For example, in order to scale to 1-million-qubit-computer, the control system would also need 1-10 million filters, circulators, and coaxial cables, occupying more than three football fields of floor space and consume roughly 40 MW of dc power (assuming no power loss associated with signal distribution). It is vital to develop miniature, low-cost, reliable, insertion loss and highly integrated microwave technologies for superconducting quantum computing for the UK to be successful in this rapidly growing sector, with a projected global market of £4B by 2024. In order to move to the 100s-qubit level and beyond, where quantum computing becomes truly useful, innovation for scalable microwave control systems is needed. A short time-window is available for the UK to invest in real-world demonstration of superconducting quantum computing. Without this, the potential for a UK researcher to lead the world in this emerging area and build strong academic and industrially facing leadership will be lost. My fellowship aims to bring modern microwave approaches to supercondcting quantum computing and demonstrate improved quantum pefromance with reduced hardware overheads and thermal loaads, paving the way to move towards 100s-qubit level, where quantum computing becomes truly useful

In the last decade, proof of concepts has been given and small-scale demonstrators have been built to show that the quantum devices allow obtaining unprecedented performances in practical applications. For example, dramatic enhancements can be obtained in the speed and computational power of next-generation computers (Quantum computing) using superconducting qubits. Also, disruptive performance improvements can be achieved in advanced imaging, remote sensing, long distance/secure communication (quantum cryptography) or diagnostic techniques using superconducting nanowire single-photon detectors - SNSPDs. The transition from demonstrators to practical scaled-up devices with a large number of elements is still at an early stage and a significant technological leap is required for a real breakthrough in those fields. The identified challenge in scaling-up the number of elements in quantum circuits, that is virtually identical for superconducting qubits and SNSPDs operating in Radio Frequency regime - RF-SNSPDs -, is represented by efficient multiplexing of these elements since they typically operate at cryogenic temperatures and need multiple connections for control and read-out at microwave frequencies. This makes the electronics complex, costly and difficult to scale beyond 10 to 100 of elements in the commercially available cryostats hampering their use in real-world applications. Single Flux Quantum (SFQ) electronics can operate at cryogenic temperature with unrivalled high frequency and ultra-low power consumption relying on the peculiar current to voltage relation of their basic element: the Josephson Junctions (JJ). Under proper condition, JJs generates ~2 ps width voltage pulses at repetition frequency above 500 GHz, with unprecedented time accuracy, stability and low power consumption. SFQ electronics is intrinsically scalable and we propose to use generated SFQ pulses as a source for precise and low noise frequency signals for multiplexed control and read-out of on-chip integrated qubits and RF-SNSPDs arrays. This transformative approach will allow to finally fill the gap in the existing quantum technology for a step-change at the same time in quantum science and advanced sensing applications. At this aim, we will bring together top UK expertise in nanofabrication and superconducting quantum technology, backed by a strong commitment from the UK world-leading company in SFQ electronics and quantum technologies SeeQC UK. We build on previous work carried out through Innovate UK, Marie Curie, Royal Society and European Research Council funding and make complimentary use of expertise and nanofabrication facilities to significant progress in the development of quantum technology in a 3-years targeted programme. Thanks to the strategic collaboration with National UK Quantum Technology Hubs, we will carry out joint experiments in quantum computing/simulation (Hub in Quantum computing and simulation - HQCS) and in advanced imaging (QuantIC) applications to show the game-changing nature of developed technology. Also, we will leverage support to engage closely with end-users and stakeholder maximizing the impact of the research project. Potential markets for developed technology will be exploited through the collaboration with QT hubs industry partners' network and with the strategic Industrial partners of this proposal like Kelvin Nanotechnology (KNT), Oxford Quantum Circuits (OQC) and SeeQC UK. This project is designed to generate high-quality research outputs and to deploy advanced technology in the field of quantum science. The work strongly resonates with the central themes of Horizon 2020 programmes and with the UK strategic research priorities set by Research Councils. The long-term goal is to establish a world-class experimental research programme which will have a powerful cross-disciplinary impact strengthening the UK's leading position in new science and technology to generate societal and economic benefits.

The primary objective of the QC2 CDT is to train the upcoming generation of pioneering researchers, entrepreneurs, and business leaders who will contribute to positioning the UK as a global leader in the quantum-enabled economy by 2033. The UK government and industry have demonstrated their commitment by investing £1 billion in the National Quantum Technologies Programme (NQTP) since 2014. In its March 2023 National Quantum Strategy document, the UK government reaffirmed its dedication to quantum technologies, pledging £2.5 billion in funding over the next decade. This commitment includes the establishment of the UKRI National Quantum Computing Centre (NQCC). The fields of quantum computation and quantum communications are at a pivotal juncture, as the next decade will determine whether the long-anticipated technological advancements can be realized in practical, commercially-viable applications. With a wide-ranging spectrum of research group activities at UCL, the QC2 CDT is uniquely situated to offer comprehensive training across all levels of the quantum computation and quantum communications system stacks. This encompasses advanced algorithms and quantum error-correcting codes, the full range of qubit hardware platforms, quantum communications, quantum network architectures, and quantum simulation. The QC2 CDT has been co-developed through a partnership between UCL and a network of UK and international partners. This network encompasses major global technology giants such as IBM, Amazon Web Services and Toshiba, as well as leading suppliers of quantum engineering systems like Keysight, Bluefors, Oxford Instruments and Zurich Instruments. We also have end-users of quantum technologies, including BT, Thales, NPL, and NQCC, in addition to a diverse group of UK and international SMEs operating in both quantum hardware (IQM, NuQuantum, Quantum Motion, SeeQC, Pasqal, Oxford Ionics, Universal Quantum, Oxford Quantum Circuits and Quandela) and quantum software (Quantinuum, Phase Craft and River Lane). Our partners will deliver key components of the training programme. Notably, BT will deliver training in quantum comms theory and experiments, IBM will teach quantum programming, and Quantum Motion will lead a training experiment on semiconductor qubits. Furthermore, 17 of our partners will co-sponsor and co-supervise PhD projects in collaboration with UCL academics, ensuring a strong alignment between the research outcomes of the CDT and the critical research objectives of the UK quantum economy. In total the cash and in-kind contributions from our partners exceed £9.1 million, including £2.944 million cash contribution to support 46 co-sponsored PhD studentships. QC2 will provide an extensive cohort-based training programme. Our students will specialize in advanced research topics while maintaining awareness of the overarching system requirements for these technologies. Central to this programme is its commitment to interdisciplinary collaboration, which is evident in the composition of the leadership and supervisory team. This team draws expertise from various UCL departments, including Chemistry, Electronics and Electrical Engineering, Computer Science, and Physics, as well as the London Centre for Nanotechnology (LCN). QC2 will deliver transferable skills training to its students, including written and oral presentation skills, fostering an entrepreneurial mindset, and imparting techniques to maximize the impact of research outcomes. Additionally, the programme is committed to taking into consideration the broader societal implications of the research. This is achieved by promoting best practices in responsible innovation, diversity and inclusion, and environmental impact.

Over the next few decades, quantum computing (QC) will transform the way we design new materials, plan complex logistics and solve a wide range of problems that conventional computers cannot address. The Hub for Quantum Computing via Integrated and Interconnected Implementations (QCI3) brings together >50 investigators across 20 universities to address key challenges, and deliver applications across diverse areas of engineering and science. We will work with 27 industrial partners, the National Quantum Computing Centre, the National Physical Laboratory, academia, regulators, Government and the wider community to achieve our goals. The Hub will focus on where collaborative academic research can make transformative progress across three interconnected themes: (T1) developing integrated quantum computers, (T2) connecting quantum computers, and (T3) developing applications for them. Objectives for each are outlined below. (T1) Developing integrated quantum computing systems, with a goal of creating quantum processors that will show real utility for specific problem examples. Objectives: OB1.1: Demonstrate quantum advantage in analogue platforms with neutral atoms and photons OB1.2: Make neutral atom quantum simulation platforms available in the cloud OB1.3: Develop new applications for these and other near-term systems (T2) A key challenge of building the million qubit machines of the future is that of 'wiring' together the quantum processors that will create such a machine. The Hub will develop technologies that help achieve this and develop models to understand how such machines will scale. Objectives : OB2.1: Develop interconnect technologies for quantum processors OB2.2: Demonstrate blind computing and multi-component networks with trapped ion quantum computers OB2.3: Demonstrate transduction and networking of superconducting processors (T3) Developing applications in science and engineering, including materials design, chemistry and fluid dynamics. Objectives: OB3.1: Develop new methods for materials and chemical system modelling and design, fluid dynamics, and quantum machine learning OB3.2: Identify the nearest routes to quantum advantage for these application areas OB3.3: Develop implementations of these algorithms on T1 and T2 Hardware These will be supported by work in overarching tools (T4) that can be used across the themes of the Hub, including error correction, digital twins, verification and software stack optimisation. Skills and training Hub partners will work with end-users, our students and researchers, and partners across the UK National Quantum Technologies Programme (UKNQTP) to ensure members of the Hub have the skills they need. Specific objectives include: Provide training in innovation, commercialisation and IP, Equality, Diversity and Inclusion and Responsible Research and Innovation (RRI) to Hub partners Provide reports and training to end-users, working in partnership with the NQCC and others Continue to provide advocacy and advice to policy makers, through work in such areas as RRI Exploitation and Engagement: The Hub will build on the strong engagement activities of the UK programme, further developing the technology pipeline. We will play a key role in strengthening and expanding the UK ecosystem through events, networking and education. Specific goals are to: Broaden the partnership of the Hub, bringing new academic, government and industrial partners into the Hub network Contribute to regulation and governance through programmes of work in standards and RRI, and close collaboration with UKNQTP partners Support the generation and protection of intellectual property within the Hub, and its exploitation Develop Hub and cross-Hub outreach initiatives, working with the RRI team, to help ensure the potential of quantum computing for societal benefit can be realised

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.