QKD in Space

Why does QKD matter to the Space sector?

There is growing international interest and investment around Satellite QKD, creating global market opportunities.

Early large-scale QKD deployment will be over optical fibre. But quantum keys cannot be transmitted through undersea cables over long distances as photons are lost and cannot pass through the optical amplifiers used in underwater cables. The only way to create global QKD-secured communications will be with satellites.

Although there is some photon loss in the atmosphere, it is low enough that we can send quantum light signals between satellites and ground stations.

To make this work, we need to collaborate with the space industry to develop new technology and infrastructure to transmit and receive quantum keys between ground stations, satellites and other aerial vehicles. As the technology advances, the space sector will become relied upon to launch and manage the QKD satellites that will become an integral part of the world’s future communications infrastructure.

Where are we now and where are we going?

There are two approaches to satellite QKD. The first involves a ground station sharing a quantum encoded key with a satellite, which then shares it with another ground station. This is needed where ground stations are on opposite sides of the earth, and requires that satellites be trusted by the users. The second approach shares entangled photons between two ground stations simultaneously, which can use the entanglement to create a shared key. This has the advantage that the satellite cannot steal the key so need not be trusted, but it is only viable where a satellite can see two ground stations at the same time.

In 2017, the Chinese satellite MICIUS demonstrated that photons – single and entangled – could be transmitted between satellite and ground stations, proving the concept of satellite QKD. In Phase 2 of the UK Quantum Technologies Programme, starting December 2019, the Quantum Communications Hub will undertake a significant programme of work on satellite QKD.

The aim is that within five years the UK will have demonstrated single photon QKD from Low Earth Orbit and interoperability with the ground QKD network. Within a decade we hope to have improved photon sources for high key transmission rates and demonstrate inter-satellite QKD. Beyond that we hope to develop a constellation for global QKD commercial service.

How the space sector can get involved

Quantum communications in space opens up new opportunities for the UK space sector in areas including:

  • Satellite hosts: delivery platform options, dedicated or shared (for hosted payloads);
  • Satellite systems and sub-systems: acquisition, pointing and tracking, fine steering mirrors, system and flight software
  • Quantum payloads: photonics components: lasers, non-linear crystals, detectors
  • Optimisation of size, weight and power constraints on small satellites
  • Optical Ground Stations: telescopes and mounts, tracking systems

The Quantum Communications Hub can help UK space companies get involved with such opportunities. We are running a significant satellite work programme which will include launching a research satellite to explore QKD approaches, including single photon, entangled photons, and continuous quantum light signals. The consortium includes RAL Space alongside academic and industrial partners, and is seeking additional commercial partners.

The Hub also provides access to cutting edge facilities and expertise to develop and test QKD technology, which has already supported many technical advances during Phase 1 in partnership with established companies, start-ups and spinouts.

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