The installation of memory and ‘repeater’ devices in space, to enable use of the quantum internet, have been proposed in research by the University of Strathclyde and an international collaboration.

The study suggests that quantum memories (QM), which store information in quantum form, and repeaters, which are used in the transmission of the information, can be deployed to facilitate use of advanced internet technology. This is done through distribution of quantum entanglement, a phenomenon in which two particles are interlinked, potentially at vast distances from each other.

The research showed that satellites equipped with QMs provided entanglement distribution rates which were three orders of magnitude faster than those from fibre-based repeaters or space systems without QMs.

The study has been published in the journal npj Quantum Information. It was led by Humboldt University in Berlin and also involved the Institute of Optical Sensor Systems of the German Aerospace Center (DLR) and JPL (Jet Propulsion Laboratory NASA).

Dr Daniel Oi, Senior Lecturer in Strathclyde’s Department of Physics, a partner in the research, said: “We show in this paper that this method would have much higher performance than previously proposed schemes and we identify promising physical systems with which to implement it.

“The work is connected to wider work at Strathclyde on Quantum Technologies, and in particular Space Quantum Communication research that includes several space missions due to be launched in the next few years.”

Global-scale quantum communication links will form the backbone of the quantum internet. Exponential loss in optical fibres means that there is no realistic application of this beyond a few hundred kilometres but quantum repeaters and space-based systems offer a solution to this limitation. 

The proposal in the research uses satellites equipped with QMs in low-earth orbit. It is focused on the use of quantum key distribution (QKD) for encryption and distribution, and of QMs to synchronise detection events which could otherwise have been happening by chance.

The researchers describe their study as “a roadmap to realise unconditionally secure quantum communications over global distances with near-term technologies.”

The paper states: “With the majority of optical links now in space, a major strength of our scheme is its increased robustness against atmospheric losses. We further demonstrate that QMs can enhance secret key rates in general line-of-sight QKD protocols.”

Quantum Technology Cluster is embedded in the Glasgow City Innovation District, an initiative driven by Strathclyde along with Glasgow City Council, Scottish Enterprise, Entrepreneurial Scotland and Glasgow Chamber of Commerce. It is envisaged as a global place for quantum industrialisation, attracting companies to co-locate, accelerate growth, improve productivity and access world-class research technology and talent at Strathclyde.

The University of Strathclyde is the only academic institution that has been a partner in all four EPSRC funded Quantum Technology Hubs in both phases of funding. The Hubs are in: Sensing and Timing; Quantum Enhanced Imaging; Quantum Computing and Simulation, and Quantum Communications Technologies.