Photons In Space!
Did you know that it’s possible to transfer secure quantum information in light using a satellite? Part of my role at the Institute for Quantum Computing at the University of Waterloo is Science Team Coordinator for Canada’s first quantum satellite mission called QEYSSat, which is the Quantum EncrYption and Science Satellite. This Canadian Space Agency (CSA) mission is a technology demonstration of a quantum uplink from ground-to-space using a satellite in low earth orbit (LEO).
But wait… what does all that mean?! A quantum uplink is where a quantum transmitter is on the ground that sends a quantum signal up to the satellite where it gets measured. This quantum signal is made up of single photons, which are indivisible energy packets of light. You can think of them like particles of energy that cannot be split. For example, a standard light bulb gives off roughly a million trillion photons a second, so you can imagine how dim just one photon is!
Using single photons, QEYSSat will demonstrate quantum communication with a quantum receiver onboard the satellite in space. The quantum receiver includes a telescope that will collect the single photons coming from the ground, and feed them to the special quantum detectors that are sensitive enough to see them. These detectors are constantly being exposed to space radiation while in LEO that will eventually make them stop working. We have some tricks to prolong their lifetime so the QEYSSat mission will last at least two years, hopefully much longer.
So why is the government investing money into quantum? The QEYSSat mission is a very important step forward for Canada’s quantum industry. It allows the government and industry to test how their technologies could work in building Canada’s quantum internet. Additionally, it could enable future-proof, unhackable communication that is of great consequence to our national security. Good thing there are great scientists working to keep our country at the cutting edge of this exciting, new technology!
There is a lot of special equipment and expertise that go into experiments like this. Quantum physics is challenging enough to do on land, so adding in tracking and linking to a rapidly moving satellite makes it even more tricky. There were a few uplink demonstrations to a moving quantum receiver achieved before the CSA announced the QEYSSat mission in 2018. This early work included establishing a quantum link from the ground to a receiver mounted inside a National Research Council Canada (NRC) research airplane. You can see the plane streaking overhead in the night sky with our trailer and quantum transmitter telescope on the ground. There was a bright visible beacon laser used to help with tracking, which you can see glowing green. Also, the airplane door had to be removed so the receiver telescope could see the quantum signal from the ground.
It takes a lot of dedicated and talented people to make these experiments work. We are about two years from the projected launch date of QEYSSat in mid 2025. A lot of preparation and testing is happening now, with more exciting work to come!