Efficient Quantum Key Distribution

Research question
Coherent communication with quadrature modulated light is a well-developed communication scheme for conventional 100G internet traffic. But, at extremely low signal strength, inherent quantum features of light such as vacuum noise dominate and prevent the exchange of meaningful messages. However, it is possible to harness and exploit this quantum uncertainty to make it useful for secure key distribution. Continuous Variable Quantum Key Distribution (CV-QKD) is such a quantum technology which is also highly efficient for deployment in DWDM networks such that quantum and conventional channels can co-exist.
CV-QKD Local Local Oscillator (LLO) schemes that converge to coherent communication have recently been gaining interest. They open up an excellent opportunity for testing and evaluating the performance of coherent communication techniques for distributing quantum signals. However, recent demonstrations of these approaches have been limited to low loss channels with reduced key rates, due to elevated receiver noise.
Approach/Methodology
This project aims to develop new CV-QKD LLO schemes for high channel loss applications with enhanced secure key rates. One direction of this work will be to recover the quantum signal information from a noisy coherent receiver. Within this project, the student will work on measurement of the quantum channel at very low receiver noise to demonstrate the potential for high performance operation. Noise reduction and optimization of CV-QKD parameters will be the major consideration for this development. This study will be extended to multi transmitter or multidimensional quantum signal detection to enhance the secure key bandwidth.
The work on the link will initially focus on measuring the noise and then extrapolating to the possible secure key rate under various quantum attacks. However, once this initial phase is complete the student will then work on a link that distils a real secure key that can be used to encode conventional channels on the existing Cambridge quantum network. Later in this project, the feasibility of extended to a national scale using the National Dark Fibre Facility will be investigated. This research is primarily experimental, using the Cambridge CV-QKD system, but moderate theoretical study is also necessary. It will be linked to the major EPSRC Quantum Technology Hub, QComm2.

The impact of the CDT in Connected Electronic and Photonic Systems is expected to be wide ranging and include both scientific research and industry outcomes. In terms of academia, it is envisaged that there will be a growing range of research activity in this converged field in coming years, and so the research students should not only have opportunities to continue their work as research fellows, but also to increasingly find posts as academics and indeed in policy advice and consulting.

The main area of impact, however, is expected to be industrial manufacturing and service industries. Relevant industries will include those involved in all areas of Information and Communication Technologies (ICT), together with printing, consumer electronics, construction, infrastructure, defence, energy, engineering, security, medicine and indeed systems companies providing information systems, for example for the financial, retail and medical sectors. Such industries will be at the heart of the digital economy, energy, healthcare, security and manufacturing fields. These industries have huge markets, for example the global consumer electronics market is expected to reach $2.97 trillion in 2020. The photonics sector itself represents a huge enterprise. The global photonics market was $510B in 2013 and is expected to grow to $766 billion in 2020. The UK has the fifth largest manufacturing base in electronics in the world, with annual turnover of £78 billion and employing 800,000 people (TechUK 2016). The UK photonics industry is also world leading with annual turnover of over £10.5 billion, employing 70,000 people and showing sustained growth of 6% to 8% per year over the last three decades (Hansard, 25 January 2017 Col. 122WH). As well as involving large companies, such as Airbus, Leonardo and ARM, there are over 10,000 UK SMEs in the electronics and photonics manufacturing sector, according to Innovate UK. Evidence of the entrepreneurial culture that exists and the potential for benefit to the UK economy from establishing the CDT includes the founding of companies such as Smart Holograms, PervasID, Light Blue Optics, Zinwave, Eight19 and Photon Design by staff and our former PhD students. Indeed, over 20 companies have been spun out in the last 10 years from the groups proposing this CDT.

The success of these industries has depended upon the availability of highly skilled researchers to drive innovation and competitive edge. 70% of survey respondents in the Hennik Annual Manufacturing Report 2017 reported difficulty in recruiting suitably skilled workers. Contributing to meeting this acute need will be the primary impact of the CEPS CDT.

Centre research activities will contribute very strongly to research impact in the ICT area (Internet of Things (IoT), data centre interconnects, next generation access technologies, 5G+ network backhaul, converged photonic/electronic integration, quantum information processing etc), underpinning the Information and Communications Technologies (ICT) and Digital Economy themes and contributing strongly to the themes of Energy (low energy lighting, low energy large area photonic/electronics for e-posters and window shading, photovoltaics, energy efficient displays), Manufacturing the Future (integrated photonic and electronic circuits, smart materials processing with photonics, embedded intelligence and interconnects for Industry 4.0), Quantum Technologies (device and systems integration for quantum communications and information processing) Healthcare Technologies (optical coherence tomography, discrete and real time biosensing, personalised healthcare), Global Uncertainties and Living with Environmental Change (resilient converged communications, advanced sensing systems incorporating electronics with photonics).