Quantum uplinks to Earth-orbiting satellites will necessitate single-photon detector technology that is robust to space radiation for the lifetime of the satellite. In this study, we experimentally assessed the effect of such radiation on a targetted selection of candidate detectors, with a focus on their impact to quantum key distribution. We then attempted to mitigate these effects, using thermal controls including deep cooling (during operation) and high-temperature annealing. Our results show that such techniques can maintain useful performance significantly beyond the one-year baseline lifetime.

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This paper describes work I mentioned earlier. We successfully demonstrated quantum key distribution with signals transmitted from a ground station to a receiver on board a flying airplane. Our receiver (which is significantly upgraded in comparison to our prior truck demonstration) was designed and largely custom-built to have a clear path to flight on a satellite. Our demonstration illustrates the viability of such a payload.

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Some context:

• Ministers Bains and Garneau celebrate $80.9 million for the Canadian Space Agency.
• Canada's support will help Waterloo launch quantum research into space.
• Statement on Government of Canada support for quantum space innovation.

I've been involved with the QEYSSat project, working on studies and prototypes, for the last 6 years. It's wonderful to see it selected as one of the two projects to receive funding, thereby allowing it to become an actual mission. Very exciting times!

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September of 2016 was a busy month for a few reasons, one of these being the two weeks I was (with the rest of our IQC team) in Smiths Falls outside Ottawa conducting trials of our prototype quantum key distribution system. Ultimately this involved transmitting quantum signals from our ground-station quantum source to our receiver on a flying NRC aircraft—quite successfully, I might add. In the intervening time to now (and modulo one vacation to Australia and New Zealand) we wrote-up our results into a paper, the pre-print of which recently appeared on the arXiv.

At the same time (not coincidentally) an article about our work appeared in the Canadian newspaper The Globe and Mail—page 1 on Dec. 21, in our region—as well as the Waterloo Region Record (pg. 2, Dec. 22). You can read the online edition of the article.

So that's neat.

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We take our quantum key distribution system out of the laboratory and mount it in the back of a small truck. Integrating a two-axis pointing system at both sites, polarization correction, and time-of-flight compensation, we demonstrate quantum key distribution from a stationary transmitter to a receiver moving at an angular speed (relative to the transmitter) equivalent to the maximum angular speed of a typical low-Earth-orbit satellite.

Bonus: Read the IQC's news release, which covers both this and the previous paper for a general audience.

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Fundamental laws of quantum physics guarantee the security of encryption keys generated through quantum key distribution, in contrast to standard encryption techniques which rely on assumptions about an eavesdropper's computational ability. That said, special technology is necessary to facilitate quantum key distribution transmissions between parties that are more than a couple of hundred kilometers apart.

A near-term solution is to use an orbiting satellite as a trusted quantum receiver. Here we detail specifically chosen algorithms that make up an implementation of quantum key distribution, suitable for a satellite receiver platform. We examine these algorithms' computational requirements while demonstrating them experimentally as we emulate the variable channel losses that would be experienced during a satellite pass (following those we published about previously).

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