7 Feb 2025

 

“If we can reduce its cost, expand its range and enhance its reliability, we can make secure quantum communication a practical reality for many different kinds of users” 

 

An expert in creating sources of entangled and hyper-entangled photons, the University of Toronto’s Li Qian is working to make ultra-secure quantum communication practical and accessible – particularly over long distances.

“Whether it’s about protecting banking information or safeguarding the signals that control critical infrastructure, there is a lot of interest in secure communication these days,” says Qian, a professor in the Edward S. Rogers Sr. department of electrical and computer engineering in the Faculty of Applied Science & Engineering.

“In quantum communication, we leverage phenomena from quantum physics to ensure that nobody can listen in or alter the message. But establishing quantum links over very large distances poses special challenges, and that’s particularly relevant for a geographically large country like Canada.” 

Qian is one of several U of T researchers who recently received new funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) and UK Research and Innovation (UKRI) to advance  projects related to quantum communication networks, quantum computing and more (See the full list of researchers below).

Establishing a quantum link typically involves creating photons that are interrelated via a quantum phenomenon known as entanglement. Once two or more photons are entangled, their quantum properties match in a way that can’t be altered. Measuring or attempting to copy one of the photons instantly affects the photon as well as its entangled partner, rendering any attempt to listen in on the signal detectable. 

But sending entangled photons through traditional optical communications networks is far from straightforward. 

“Optical fibres are the best technology we know of for long-distance communication, because the losses are very low,” says Qian. “But at the same time, the losses are not zero, so by the time you have gone a hundred kilometres, you’ve lost 99 per cent of the photons. 

“With classical signals, that’s not a problem, because you can add amplifiers along the way that boost the signal as it degrades. But if you’re only sending single photons, which is the case in quantum communication, that is very hard to do.” 

Two of Qian’s newly-funded projects involve collaborations with Canadian researchers and companies to create long-distance quantum links for secure communications, particularly in the area of defence. 

She is also working with researchers at the University of Bristol to study how principles and paradigms from classical optical networks can be adapted for quantum networks. 

“My collaborators know a lot about how to package signals, or how to dynamically reconfigure the network to deal with high-traffic situations,” Qian says. 

“We are looking at how you approach these challenges differently once you start sending entangled photons.” 

Qian is also part of a collaboration between Canadian and European researchers known as HyperSpace, which aims to use satellites to establish transcontinental quantum networks. 

“As in any industry, customers want a range of solutions to meet their various needs,” says Qian. 

“If we can reduce its cost, expand its range and enhance its reliability, we can make secure quantum communication a practical reality for many different kinds of users.” 

 

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Li Qian of in the Faculty of Applied Science & Engineering is one of several U of T researchers who recently received funding from NSERC and UK Research and Innovation