The Canadian Government has announced that one of their research teams have made significant progress towards enabling secure quantum communication via moving satellites. The study, published in the journal Quantum Science and Technology, demonstrates the first quantum key distribution transmissions from a ground transmitter to a quantum payload on a moving aircraft.
With anticipated satellite mission, the team at the Institute for Quantum Computing (IQC) and Department of Physics and Astronomy of University of Waterloo, Ontario, designed their prototype receiver to consist of components compatible with the size and operating environment restrictions of a micro satellite.
According to the researching team, Quantum key distribution (QKD) establishes cryptographic keys between two distant parties in a way that is crypt-analytically unbreakable. Ground based QKD systems use optical fibre links, and are limited to distances of a few hundred kilometers due to absorption losses, which get exponentially worse as the distance increases.
Free space links have been shown to work over ground with varying distances, both in stationary and moving tests. But despite losses due to geometric effects scaling quadratically with distance, the addition of atmospheric absorption and turbulence and the need to have clear line of sight mean terrestrial free-space transmissions are also limited to a few hundred kilometers. Satellite based systems can expand quantum communication to a global scale.
To test their system, the team used the Twin Otter aircraft of the National Research Council to carry out 14 passes over their ground transmitting station at varying distances, achieving a quantum signal link for seven passes, and a secret key extraction for six of the seven successful passes.
They achieved optical links at similar angular rates to those of low-Earth-orbit satellites, and for some passes of the aircraft over the ground station; links were established within 10 seconds of position data transmission. They saw link times of a few minutes and received quantum bit error rates typically between three and five per cent, generating secure keys up to 868 kb in length.
With a proven concept, the team believes that the results would now provide a blueprint for future satellite missions to build upon and is also just in time for the announcement of the quantum satellite mission by the Canadian Government.
