Space Quantum Communication

The distribution of quantum states and resources are crucial for many applications of quantum technologies including secure communications, networked quantum computers, distributed sensors, and enhanced positioning, navigation, and timing. Space-based systems are under development in order to demonstrate space quantum communications, particularly quantum key distribution (QKD) on a global scale.

Terrestrial QKD has already begun to be commercialised and deployed on optical fibre networks. These point-to-point links currently have limited range due to the exponential reduction in signal due to absorption in glass. The development of quantum memories and repeaters to overcome these limits is still at a relatively early stage. As a result, free-space transmission using satellites is an attractive alternative for spanning the Earth as well as to service mobile or remote end-points.

Pioneering demonstrations by the QUESS mission and the Micius satellite have spurred intense international activity to develop and deploy satellite QKD. The UK has several satellite QKD missions in development, including one of Strathclyde’s partners the Quantum Technology Hub in Quantum Communications. Their aim is to launch and operate a CubeSat to demonstrate a UK QKD payload and distribute encryption keys to optical ground stations.

The main issue with satellite QKD is the limited amount of time that a low Earth orbit satellite is in view of an optical ground station, hence the volume of raw key signals that can be exchanged is restricted. Hence finite block size effects due to statistical fluctuations and uncertainty are crucial in the analysis of the rate and security of secret keys to be distributed. Additionally, the dynamic configuration of satellite constellations complicates the optimisation of establishing secure links between multiple network end-points through key swapping under changing and uncertain traffic loads. The aims of the project include the optimisation of protocols for satellite QKD and the elucidation of the implications for the design and operation of large-scale quantum communication constellations.

Funding

The project will be as part of the QT Hub in Quantum Communications where Strathclyde is leading modelling and analysis activities as part of the Hub mission to launch and operate a quantum CubeSat. CNQO also leads development of the Satellite Quantum Modelling and Analysis (SatQuMA) software suite https://cnqo.phys.strath.ac.uk/research/quantum-information/satquma/