Today it is common admitted that the future of computer science will be related to the quantum sphere. Companies like Google, Microsoft, IBM and several well-funded startups are feverishly building quantum computers and routinely clamoring for advances that seem to put this exotic, world-changing technology within reach. In 1979, all this was unthinkable. But this summer, two scientists met in the Atlantic Ocean off the coast of Puerto Rico, and their underwater conversation led to the work that resulted in quantum information theory. In a broader sense, their contributions helped bring computing into the quantum era.
These water-soaked scientists, Charles Bennett and Gilles Brassard, are now the newest recipients ACM AM Turing AwardNobel Prize in this field.
Until this meeting in 1979, there was a disconnect between computer science and physics. The latter field saw a breakthrough in the early 20th century when physicists discovered quantum mechanics, a deeper explanation of how the universe works that replaced Isaac Newton’s classical physics. However, computer science did not concern itself with the quantum world, except to deal with its effects on petite chips, where the behavior of electrons was essential.
“In the 1950s and 1980s, people thought that quantum effects occurred in very small objects and were the source of noise. To build transistors, you had to know quantum theory,” explains Bennett. “People thought quantum mechanics was a nuisance.” He and Brassard discovered methods – such as quantum coin flips and quantum entanglement – that turned the perceived limitations of quantum reality into a powerful tool.
At the time of their meeting, Bennett was at a career crossroads; joined IBM in 1973 but took a multi-year hiatus from academic publishing. One source of continuing fascination was the idea of a fellow student, Steven Weisner, that using a quantum form of cryptography could enable digital money that could not be counterfeited. (Yes, Weisner had a vision for cryptocurrency in the tardy 1960s!) At a 1979 conference, Bennett noticed that a cryptologist named Brassard was present – he had just completed a dissertation on public-key cryptography – and located him overseas.
“So I was swimming on the beach when a complete stranger came up to me and started telling me that his friend had discovered that, thanks to quantum mechanics, we could produce inexpensive bank notes out of thin air,” Brassard says. “If I were on solid ground, I would have run for my life, but I was trapped in the ocean, so I listened politely.” Although Brassard had no prior interest in physics, he was intrigued by the approach, and the two eventually published a theory called BB84, essentially creating an alternative to classical public key cryptography based on what became quantum information theory. Suddenly, the quantum world is a source of solutions – if scientists can invent the mechanisms that make it possible. As Yannis Ioannidis, president of the ACM, which awards the Turing Award, put it in a statement: “Bennett and Brassard have fundamentally changed our understanding of information itself.”
Both scientists take pains to ensure that their original work did not directly lead to the current scramble to build quantum computers. Bennett notes that v conference at MIT in 1981, legendary physicist Richard Feynman “stressed that since nature is quantum, some computational tasks would probably have to be performed by a quantum computer.” He also credits physicist David Deutsch with key ideas about quantum computing. Bennett and Brassard became part of this effort.
“Quantum computing was invented independently of us, but then we stepped in,” Brassard says. “I was the first person to design a quantum circuit for quantum teleportation.” Brassard and Bennett work on teleportationalthough still in the experimental phase, it is now part of quantum knowledge. Armlet he said that “this will one day power the quantum internet.”