Implementation of global-scale quantum communication networks is currently hampered by distance limitations affecting the quality of signals sent down standard optical fibre. Use of quantum repeaters can help to extend the transmission range, but the resulting technology requirements and costs are substantial.
In a newly published paper, Quantum Communications Hub researchers from the University of Strathclyde, in collaboration with colleagues from Humboldt University of Berlin in Germany, are proposing a visionary new model using satellites as hosts of quantum memories, with demonstrably improved results.
The use of large satellite constellations to extend quantum secure communications at inter-continental scales has previously been studied. Indeed, it is expected that space-borne quantum technologies such as quantum repeaters and memories will provide the necessary infrastructure for truly global, future-proof networks. However, these solutions also come with expensive hardware and system complexity overheads, currently limiting their commercialisation potential.
The new approach proposes the use of a single orbiting satellite bearing two quantum memories of different lifetimes – a longer- and a shorter-lived one – thus acting as a time-delayed version of a quantum repeater. The proposed setup has obvious advantages in terms of reduced system complexity and correspondingly lowered costs. Furthermore, it also results in substantially improved distribution rates of long-distance entanglement distribution and thus encryption keys.
Both entanglement distribution and quantum memories are key applications of quantum physics, necessary for the realisation of a so-called quantum internet, as well as real-world implementation of practical quantum secure communication networks, enhanced positioning, navigation, and timing systems, and distributed quantum sensing technologies.
The new model leverages significant progress in extending quantum memory storage times to greatly expand entanglement distribution ranges and in so doing, helps provide realistic technology solutions for networked quantum technologies at global scale, with commercialisation potential.
University of Strathclyde’s Daniel Oi, who helped lead this work and is also Director of the EPSRC International Network in Space Quantum Technologies, said: “Satellites will provide crucial links in the global quantum internet. This new method greatly simplifies the logistics of creating quantum connections between widely spread locations.”
The lead author of the study, Mustafa Gündoğan from HU Berlin, adds: “In this work, we combined two separate paradigms in quantum information science for the first time: quantum repeater behaviour and the physical transportation of qubits, which resulted in potential improvements by many orders of magnitude over existing protocols.”
Gündoğan M, Sidhu JS, Krutzik M, Oi DKL. “Time-delayed single satellite quantum repeater node for global quantum communications”. Optica Quantum 2, 140-147 (2024) DOI: 10.1364/OPTICAQ.517495
