- Born:
- April 20, 1955, Montreal, Quebec, Canada (age 71)
- Awards And Honors:
- Order of Canada (2013)
Gilles Brassard
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Who is Gilles Brassard?
Gilles Brassard, born in Montreal, Canada, on April 20, 1955, is a distinguished Canadian computer scientist celebrated for his contributions to quantum cryptography and quantum teleportation. He earned degrees from the University of Montreal and a doctorate from Cornell University.
Brassard co-created the BB84 quantum cryptography scheme with Charles Bennett, which uses polarized photons to securely transmit bits, ensuring that eavesdropping can be detected. Brassard, Bennett, and others also described how to teleport a quantum state from one subatomic particle to another using quantum entanglement.
His honors include the Herzberg Medal (2009), the Order of Canada (2013), and the Wolf Prize (2018).
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What is Gilles Brassard known for in science?
Gilles Brassard, a Canadian computer scientist born in Montreal, is renowned for his contributions to quantum cryptography and quantum teleportation. His most notable achievement is the co-invention of the BB84 quantum cryptography scheme in 1984, with Charles Bennett. This scheme uses polarized photons to represent bits, ensuring secure communication between parties.
Brassard, along with Bennett and collaborators, also published research in 1993 on quantum teleportation, detailing how to transfer a quantum state between subatomic particles using quantum entanglement.
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What is quantum cryptography?
Quantum cryptography is the science of secure communication using quantum mechanics. It includes cryptography, which is how information is concealed and encrypted, and cryptanalysis, which is how encrypted information is revealed when the secret key is unknown.
The first quantum cryptography scheme, BB84, was created by Gilles Brassard and Charles Bennett in 1984. In BB84, Alice sends Bob single polarized photons to represent bits. Half of the photons are polarized in a horizontal-vertical basis, and the other half are polarized in a diagonal basis. Bob measures the photons and tells Alice which basis he used. Alice then tells him when they used the same basis, and they use those bits as their key.
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How did Gilles Brassard contribute to quantum cryptography?
Gilles Brassard, a Canadian computer scientist, significantly contributed to quantum cryptography through his co-invention of the BB84 quantum cryptography scheme with Charles Bennett.
BB84 allows secure communication between parties, named Alice and Bob, by using polarized photons to represent bits. Alice sends Bob single photons polarized in either a horizontal-vertical basis or a diagonal basis. Bob measures the photons in either basis, and after the measurements, Bob tells Alice which basis he used. Alice then tells Bob when they used the same basis, and they keep those bits as their key. To detect eavesdropping, Alice sends a piece of the key to Bob; if an eavesdropper is present, they would introduce errors that Alice and Bob can detect.
Brassard and Bennett first experimentally tested BB84 in 1989.
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What is the BB84 protocol developed by Brassard and Charles Bennett?
The BB84 protocol, developed by Gilles Brassard and Charles Bennett (hence BB84), is a quantum cryptography scheme where Alice wants to communicate securely with Bob. Alice sends Bob single polarized photons to represent bits. Half of the photons are polarized in a horizontal-vertical basis, and the other half are polarized in a diagonal basis. Bob measures the photons and tells Alice which basis he used. Alice then tells Bob when they used the same basis, and they use those bits as their key. To ensure no eavesdropping, Alice sends a piece of the key to Bob. If there was an eavesdropper, that person could not know which basis the photons were being transmitted and could alter the key, alerting Bob and Alice.
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How has Gilles Brassard’s work influenced computer science and technology today?
Gilles Brassard, a Canadian computer scientist, is renowned for his contributions to quantum cryptography and quantum teleportation. His most notable work, the BB84 quantum cryptography scheme (co-created with Charles Bennett), introduced a method for secure communication using polarized photons, influencing modern cryptographic techniques.
Brassard, Bennett, and their team also described how to teleport a quantum state from one subatomic particle to another using quantum entanglement. Austrian physicist Anton Zeilinger, who successfully demonstrated quantum teleportation in 1997, won the 2022 Nobel Prize for Physics for his experiments.
Brassard's work has earned him numerous accolades, including the Herzberg Medal (2009), the Order of Canada (2013), and the Wolf Prize (2018).
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Gilles Brassard (born April 20, 1955, Montreal, Quebec, Canada) is a Canadian computer scientist known for his work in quantum cryptography and quantum teleportation.
Brassard received bachelor’s (1972) and master’s (1975) degrees in computer science from the University of Montreal and then a doctorate (1979) in theoretical computer science from Cornell University. He returned to the University of Montreal as an assistant professor in 1979 and then became a full professor in 1988.
“Imagine my surprise when this complete stranger swims up to me and starts telling me, without apparent provocation on my part, about Wiesner’s quantum banknotes! This was probably the most bizarre, and certainly the most magical, moment in my professional life.” —Gilles Brassard
After Brassard received his doctorate, he attended a conference in San Juan, Puerto Rico, where he was swimming when he was approached by American physicist Charles Bennett, who knew of his interest in cryptography. Bennett told Brassard about his friend Stephen Wiesner’s idea of using quantum mechanics to create money that could not be counterfeited. Such a banknote would contain twenty two-state quantum systems in which any attempt to measure the states and thus duplicate them would alter the states from their original configuration.
Inspired by Wiesner’s idea, Brassard and Bennett came up with the first quantum cryptography scheme, BB84, named after their initials and the year the work was published. In BB84, Alice wishes to communicate securely with Bob. To represent bits, she sends him single polarized photons. Half of all the photons are polarized in a horizontal-vertical basis; that is, bits with value 0 are horizontally polarized, and bits with value 1 are vertically polarized. The other half of the photons are polarized in a diagonal basis, with 0s being polarized at 45 degrees from horizontal and 1s being polarized at 135 degrees. Bob measures half the individual photons in the horizontal-vertical basis and half in the diagonal basis. If Alice sends a horizontal photon and Bob measures it in the diagonal setting, the reading will be either 45 or 135 degrees. After Bob measures all the photons, he tells Alice which basis he used. Alice tells him when they used the same basis. They throw out the bits for which they used a different basis and keep those that had the same basis as their key. To make sure no one is eavesdropping, Alice sends a piece of the key to Bob. If there were an eavesdropper, that person could not know which basis the photons were being transmitted in and thus could sometimes send a wrongly polarized photon to Bob. Sending the wrong photons would alter the key, and Bob and Alice would know someone was listening in. Bennett, Brassard, and their collaborators first experimentally tested BB84 in 1989, and it has even been used over a distance of 1,200 km (about 745 miles) between an artificial satellite and Earth.
Brassard, Bennett, and their collaborators published work in 1993 describing how to “teleport” a quantum state from one subatomic particle to another by using quantum entanglement. Two particles can be in a single entangled state such that measuring a property of one particle instantly determines that same property in another particle. For example, two particles are in a state in which one is spin-up and the other is spin-down. Since the second particle must have the opposite value of the first particle, measuring the first particle results in a definite state for the second particle, notwithstanding that the two particles may be millions of kilometers apart and are not interacting with each other at the time. The teleportation is done by entangling one particle in an entangled pair with a third particle. The third particle then has the properties of the other particle in the original entangled pair. Austrian physicist Anton Zeilinger and his collaborators successfully demonstrated quantum teleportation in 1997, and he won the 2022 Nobel Prize for Physics for his experiments.
Brassard has received many honors for his work, including the Herzberg Medal (2009), the Order of Canada (2013), and the Wolf Prize (2018). He has written the books Algorithmics: Theory and Practice (1988, with Paul Bratley), Modern Cryptology: A Tutorial (1989), and Fundamentals of Algorithmics (1995, with Bratley).