High performance Satellite Quantum Communication

The current public cryptography techniques are under a threat from the increasing compu-tational powers of Supercomputers and Quantum Computers. Quantum Key Distribution has emerged as a reliable symmetrical key distribution system to establish a secure communication
network as it utilises the basic principles of Quantum Physics to provide unconditional secrecy. QKD can be performed over optical bres but it is range limited due to losses in the optical - bres. Satellite/ Free space based Quantum communication(SatQKD) provides longer range and
flexible Quantum Networks. The performance of Satellite-ground QKD is limited by losses due to background noise, distraction and detection efficiency. The current satellite QKD communication networks are thus based around 785nm wavelength to minimise distraction losses and optimise detection effciency. The BB84 QKD source utilises 4 laser diodes with different polarizers, the distinguishability of the spectral or temporal performance of these laser diodes can pose a risk of Side channel attack from an eavesdropper. In this project, we can measure and upper bounded the severity of this attack experimentally. Also, to mitigate this threat we can investigate the scope of using a source with high speed photon generation and modulation. The lasers and modulation devices for 785nm are not suitable for high speed transmission, thus one approach could be to use the sources optimised for highest power emission, modulation rates and transmission at 1550nm used in the telecom industry. The idea is to up-convert the modulated signal from 1550nm to 775nm and use it for SatQKD. Such a source can cut the losses due to distraction and make the detection far more efficient leading to high speed QKD transmission (in the range of GHz). This will improve the overall performance and security of Satellite based Quantum Communication and inter-satellite QKD. Other than that, the utility of lasers in UV(<280nm) range can also be explored during the project to improve space Quantum Communication and facilitate Daylight QKD.

Our ambitions for the impact of the Quantum Engineering CDT are simple and clear: our PhD graduates will be the key talent that creates a new, thriving, globally-competitive quantum industry within the UK. In Bristol we will provide an entire ecosystem for innovation in quantum technologies (QT). Our strong and diverse research base includes strengths going from quantum foundations to algorithms, experimental quantum science to quantum hardware. What makes Bristol unique is our strong innovation and entrepreneurship focus that is deeply embedded in the entire culture of the CDT and beyond. This is reflected in our recent successful venture QTEC, the Quantum Technologies Enterprise Centre, and our Quantum Technologies Innovation Centre (QTIC), which are already enabling industry and entrepreneurs to set up their own QT activities in Bristol. This all occurs alongside internationally recognised incubators/accelerators SetSquared, EngineShed, and UnitDX.

At the centre of this ecosystem lies the CDT. We will not just be supplying existing industry with deeply trained talent, but they will become the CEOs and CTOs of new QT companies. We are already well along this path: 7 Bristol PhD students are currently involved in QT start-ups and 3 alumni have founded their own companies. We expect this number to rise significantly when the first CDT cohort graduates next year (2 students have already secured start-up positions). Equally, it is likely that our graduates will be the first quantum engineers to make new innovations in existing classical technology companies - this is an important aspect, as e.g. the existing photonics, aerospace and telecommunications industries will also need QT experts.

The portfolio of talent with which each CDT graduate will be equipped makes them uniquely suited to many roles in this future QT space. They will have a deep knowledge of their subject, having produced world-leading research, but will also understand how to turn basic science into a product. They will have worked with individuals in their cohort with very different skills background, making them invaluable to companies in the future who need these interdisciplinary team skills to bring about quantum innovations in their own companies. Such skills in teamworking, project management, and self-lead innovation are evidenced by the hugely successful Quantum Innovation Lab (QIL). The idea and development of QIL is entirely student-driven: it brings together diverse industrial partners such as Deutsche Bank, Hitachi, and MSquared Lasers, Airbus, BT, and Leonardo - the competition to take part in QIL shows the hunger by national industry for QT in general, and our students' skills and abilities specifically. With this in mind, our Programme has been co-developed with local, UK, and international companies which are presently investing in QT, such as Airbus, BT, Google, Heilbronn, Hitachi, HPE, IDQuantique, Keysight, Microsoft, Oxford Instruments, and Rigetti. The technologies we target should lead to products in the short and medium term, not just the longer term. The first UK-wide fibre-based quantum communication network will likely involve an academic-industrial partnership with our CDT graduates leading the way. Quantum sensing devices are likely to be the product of individual innovators within the CDT and supported by QTIC in the form of spin-outs. Our graduates will be well-positioned to contribute to the advancement of quantum simulation and computing hardware, as developed by e.g. our partners Google, Microsoft and Rigetti. New to the CDT will be enhanced training in quantum software: this is an area where the UK has a strong chance to play a key role. Our CDT graduates will be able to contribute to all aspects of the software stack required for first-generation quantum computers and simulators, the potential impact of which is shown by the current flurry of global activity in this area.