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A chance encounter between a computer-science professor and a physicist launches new field of quantum cryptography
February 11, 2005
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.
"All of this is thanks to Gilles," he says.
Barry Sanders, a quantum physicist who recently returned to Canada from a research post in Australia, agrees, saying Brassard has played a key role in making this country "the world leader in this field."
Brassard and Bennett's invention sprung from their discovery of how principles from the previously unlinked fields of quantum physics and computer science could be combined to establish an unbreakable secret key.
Instead of transmitting information along cables via electronic signals, they use polarized photons - tiny particles of light - that are so sensitive that when intercepted, they immediately become corrupted. This renders the message unintelligible and tips off both sender and intended recipient to the spying attempt.
What's causing particular excitement now is that the way that applications of Brassard and Bennett's technology have just been commercialized and put to market.
Since late 2003, consumers have been able to acquire quantum cryptographic systems that make short-haul computer links unbreakable to spies. The systems are being sold by two competitors in Geneva and New York for as little as $70,000 U.S. Both firms' devices use Brassard and Bennett's seminal insight....Continued
But that's only a start, Laflamme says. "The potential is absolutely enormous."
- - -
Intrigued during their chance encounter off the shores of Puerto Rico by the idea of impossible-to-forge bank notes, the two men repaired to air-conditioned restaurants and cafes where they tossed it around some more.
They left the island firm friends, returning, respectively, to Montreal and Croton-on-Hudson, a village just north of New York City, where they continued their brainstorming.
While the anti-counterfeiting idea ultimately proved impractical, both scientists soon realized that one of its underlying principles - a theory that exploited the unique properties of photons - could be applied more broadly to code making.
Cryptography has always been a race between code-makers and code-breakers.
Today's most sophisticated codes, used for the protection of information on computers, rely on hugely complex mathematical calculations that present-day computers aren't believed to be powerful enough to solve.
Yet as Brassard explains, it's possible someone has already figured out how to crack these codes. If so, such a person might want to keep this quiet so as to benefit personally, Brassard remarked, although there could also be an altruistic reason for doing so.
"Society would collapse, electronic commerce would collapse," Brassard says. "There would be chaos. I would keep quiet - just as I would if I found a new weapon of mass destruction."
But the biggest fear in the cryptographic world is that a new kind of super-powerful "quantum computer" could soon be constructed that would have the capacity to quickly solve the kinds of code-breaking problems that today's computers are stumped by.
Already, experts say, a U.S. mathematician, Peter Shor, has developed a formula that could be used by a quantum computer, once one has been built, to crack current encryption technology.
The prospect of such a computer being constructed obviously worries governments, business and the military - and should be of concern to all who value their privacy.
It would be "a nuclear bomb to the Internet," says Barry Sanders, director of the University of Calgary's Institute for Quantum Information Science. "All of the security that we rely on when we use the Internet would be obsolete."
And this is why Brassard and Bennett's invention is causing such a stir: theirs is the first practical form of cryptography that could not be broken, even by some yet-to-be-built quantum computer.
The key to the security of a quantum cryptography code, Laflamme explains, is that it "does not involve solving a mathematical problem; it would involve breaking the laws of physics."
Brassard and Bennett's collaboration has led to another breakthrough, too. In an invention reminiscent of Star Trek, the two physicists and their colleagues have developed a "quantum teleportation" technology that can dissemble a particle of matter in one location and beam it for reassembly in another....Continued
This technique was invented in 1992, first tested experimentally four years later with photons and is still being tested by scientists around the world.
(One of the co-inventers of the technique was Brassard's former student Claude Crepeau, who now directs his own research team in quantum information processing at McGill University.)
In 1999, the invention inspired a best-selling novel - Timeline, by Michael Crichton - and a spinoff Hollywood movie of the same name.
Filmed in Montreal and released two years ago, the storyline features protagonists being quantum-teleported back to the Middle Ages.
- - -
Brassard and Bennett's inventions have also generated enormous attention from the world science media. An October 1992 cover story in Scientific American magazine gave the duo's quantum cryptography technique its first burst of stardom.
Now, a second wave of coverage has come as experiments prove the commercial viability of their cryptography technique and fledgling new products make their way to market.
Most recently, Brassard and Bennett's cryptography technique was again the subject of a cover story - this time in the January issue of Scientific American. They've also drawn coverage from Britain's New Scientist and as well as in German, Australian and Japanese media outlets, among others.
Yet the technology still faces serious distance limitations. Photons can only travel so far before they fade. They require amplification at regular intervals if they're to be transmitted over long distances - something that has not yet proved feasible. Scientists are working hard to overcome this limitation.
So far, the record for transmitting coded messages through fibre-optic cables is 100 kilometres; the maximum distance reached to date through the air is 23 kilometres between two mountaintops.
This latter achievement is of particular significance because it's generally considered harder to transmit photons through the thicker air found near the Earth's surface than up toward space, where there's less atmospheric interference.
That's why scientists are hopeful they'll soon be able to send photons to satellites, which typically orbit 150 kilometres above the Earth. Such a development would set the stage for the launch of the world's first truly global unbreakable encrypted communications system.
So promising is the field of quantum information processing that governments and corporations around the world are investing millions of dollars in research in the field.
The first-ever local quantum-encrypted network of computers is now up and running in Cambridge, Mass., where it is managed by the pioneering Internet firm BBN Technologies Inc.
And the Los Alamos National Laboratory's quantum cryptography team has joined with six European research institutions to push the field further. In December, the team tied with another group to snag one of the world's most prestigious science prizes - the European Union's $1.3-million (U.S.) Descartes research prize - for its project to build a secure global quantum cryptographic communications system....Continued
In Canada, Research in Motion founder and co-chief executive Mike Lazaridis put up $100 million of his own money in 1999 to fund the non-profit and independent Perimeter Institute of Theoretical Physics in Waterloo, now a leading centre of quantum information research. (Two more RIM executives have since contributed another $20 million, while Ottawa and Ontario have kicked in another $54 million.)
Last month, the University of Calgary got into the act, launching its Institute for Quantum Information Science.
There have been commercial developments, too.
In 2003, a Swiss firm, id Quantique SA of Geneva, became the first to sell a quantum cryptography system to the public. Another company, New York City's MagiQ Technologies Inc., soon followed.
Yet Brassard and Bennett haven't made a penny from these ventures; they've chosen not to patent their discovery in the hopes of fostering an environment where colleagues can feel unhindered in their efforts to develop the field.
Other companies with projects in the works include IBM - where Bennett is a research fellow at the company's Yorktown Heights, N.Y., research centre - and Japanese computing giants NEC, Fujitsu and Toshiba.
So great is the interest among potential buyers that industry analyst Martin Illsley predicts the technology will be widespread in business and government settings in as little as five years.
Early adopters will likely be financial institutions, governments and telecommunications firms, said Illsley, an associate partner at consulting firm Accenture Inc., in a telephone interview from France.
Others share that optimism. In a report, International Data Corp. has predicted the market for quantum cryptography products will be about $30 million U.S. within three years - and about $300 million within 10 years.
- - -
Brassard has gathered a devoted group of researchers and students at the Universite de Montreal's computer science department.
Now 49, he grew up in Ahuntsic, where his father was an accountant and his mother taught yoga.
He credits his three older brothers - all scientists as well - with inspiring him to pursue his precocious interest in math, a precursor to his fascination with computers and physics.
A brilliant student, Brassard had entered secondary school by age 10 and was already doing his undergraduate studies at the Universite de Montreal by age 13.
At the time, he recalls, he thought there was "nothing unusual" about attending university so young. He said other students treated him well "even though I looked rather small and young for my age."
Now living in Outremont with his two daughters, Brassard says he reads, cooks and listens to classical music in his spare time.
He used to play squash and go cross-country skiing too. But these days, he says wistfully, there's no time for that. All the attention swirling about him - and the fast pace of developments in his field - keeps Gilles Brassard a very busy man....Continued
Bennett, C. H., Brassard, G. and Ekert, A. K., Quantum cryptography, Scientific American, October 1992, pp. 50-57.
Stix, G., Best-Kept Secrets, Scientific American, January 2005, pp. 78-83.
Singh, S., The Code Book: The Science of Secrecy from Ancient Egypt to Quantum Cryptography, Random House Inc., 1999.
Gilles Brassard: http://www.iro.umontreal.ca/~brassard
Charles Bennett: http://www.research.ibm.com/people/b/bennetc/home.html
Claude Crepeau: http://www.cs.mcgill.ca/~crepeau/
Raymond Laflamme: http://www.iqc.ca/people/rlaflamme/
Barry Sanders: http://qis.ucalgary.ca/~bsanders/Institutions
Universite de Montreal: Laboratoire d'Informatique Theorique et Quantique - http://www.iro.umontreal.ca/labs/theorique/
McGill University: Crypto and Quantum info lab - http://crypto.cs.mcgill.ca/
Perimeter Institute of Theoretical Physics: http://www.iqc.ca/
University of Calgary's Institute for Quantum Information Science: http://www.iqis.org/Commercial products
id Quantique SA: http://www.idquantique.com/
MagiQ Technologies Inc.: http://www.magiqtech.com/
source: Alison macgregor
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