In 1984, together with Charles H. Bennett, he invented the BB84 protocol for quantum cryptography. He later extended this work to include the Cascade error correction protocol, which performs efficient detection and correction of noise caused by eavesdropping on quantum cryptographic signals.
Gilles Brassard is one of the earliest pioneers of quantum information science in the world. His most celebrated breakthroughs are the invention of quantum cryptography and quantum teleportation, both universally recognized as fundamental cornerstones of the entire discipline. His other influential discoveries include privacy amplification, entanglement distillation, amplitude amplification and the first lower bound on the power of quantum computers. Through his visionary thinking and groundbreaking research, Professor Brassard has played a pivotal role in transforming the field of quantum information science from what was initially perceived to be merely a fringe pursuit into an area of vigorous and dynamic international activity.
On December 30, 2013 the Governor-General of Canada, the Right Honourable David Johnston, announced that Gilles Brassard has been named as an Officer in the Order Of Canada. In 2018 he received the Wolf Prize in Physics.