It began 25 years ago in the warm coastal waters of Puerto Rico when a stranger swam over to Gilles Brassard and struck up a conversation about using quantum physics to make bank notes impossible to counterfeit.

“I had no idea who he was,” recalled Brassard, then a 24-year-old prodigy and computer-science professor at the Universite de Montreal. “He just started talking nonsense about quantum physics.”

The stranger turned out to be U.S. physicist Charles H. Bennett. Their chance meeting while attending a theoretical computer science conference would end up revolutionizing the art of code making, also known as cryptography.

Together, Brassard and Bennett would go on to found a field of science – quantum information processing – whose effects on society some say could even rival the impact that the steam engine had in its time.

Already, experts agree, Brassard and Bennett’s most famous invention, a technique known as quantum cryptography, is set to eliminate terrifying vulnerabilities that could soon arise in the way governments, banks, the military, business and the public use computers and the Internet to communicate and store data.

Some observers see the technology as one day making the Internet secure enough that medical professionals could share confidential health data online in ways that would be insecure now.

Yet for all its promise, this invention is also making governments nervous.

The ability to send unbreakable coded messages could just as easily be exploited, authorities fear, by criminals and terrorists who now lack a foolproof way of avoiding having their messages cracked.

In the midst of all this excitement and controversy is Montreal-based Brassard, who has made Canada a world leader in his fast-growing field.

Because of him, Canada “has turned out to be the best place in the world” to do research in quantum information processing, says physicist Raymond Laflamme, a leading figure in the field who recently returned to Canada from a post with the U.S. Department of Energy’s Los Alamos National Laboratory.

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