In 1984, Charles Bennett and Gilles Brassard published a paper that most people ignored. They proposed a method for two parties to share a secret encryption key using quantum particles. The idea seemed impractical. The lasers were too weak. The detectors were too noisy. The whole thing looked like a theoretical curiosity.
Forty-one years later, that curiosity has earned them the Turing Award.
The Association for Computing Machinery announced this week that Bennett and Brassard will receive the 2025 Turing Award, often called the Nobel Prize of Computing. The award recognizes their foundational work in quantum information science — a field that barely existed when they started.
Bennett is an American physicist and an IBM Fellow. He spent his career at IBM Research asking a strange question: What does physics have to do with information? The answer, it turned out, was everything.
His collaboration with Brassard produced BB84, the first quantum cryptography protocol. The protocol uses individual photons to generate a shared random key. If anyone intercepts those photons, the quantum state changes. The parties know they have been compromised. It is the first cryptographic system whose security rests on the laws of physics, not on the difficulty of solving a math problem.
That distinction matters. Classical encryption relies on problems like factoring large numbers. Quantum computers, if they become powerful enough, could solve those problems trivially. Quantum cryptography offers a different path — one that does not depend on assumptions about an attacker’s computing power.
Bennett also formulated what are now called the four laws of quantum information. These principles govern how quantum information can be manipulated, copied, and transmitted. They have become a standard framework for researchers working in the field.
His work on reversible computing and cellular automata opened other lines of inquiry. Reversible computing asks whether computation can be done without generating heat. The question has practical implications for energy-efficient processors. Cellular automata, meanwhile, explore how simple rules can produce complex behavior — a topic that connects computing to physics, biology, and philosophy.
The award comes at a moment of intense activity in quantum technology. Governments and corporations are pouring billions into quantum computing research. China has launched a quantum communications satellite. Google and IBM are racing to build error-corrected quantum processors. Bennett and Brassard’s 1984 paper is now one of the most cited in computer science.
But the path was not obvious. For years, quantum information theory was a niche pursuit. Few researchers understood it. Fewer still believed it would lead to practical technology. Bennett kept working. He re-examined the physical basis of information, applying quantum physics to problems of information exchange. He helped turn an esoteric subfield into a discipline that now has its own journals, conferences, and departments.
The Turing Award is the latest in a series of honors for the pair. They have previously received the Breakthrough Prize in Fundamental Physics and the Wolf Prize in Physics. But the Turing carries special weight in computing. It places them alongside pioneers like Alan Turing himself, John McCarthy, and Tim Berners-Lee.
Bennett’s influence extends beyond his own publications. He trained and inspired a generation of quantum information scientists. Many of them now lead their own research groups. The field he helped create is growing faster than ever.
Brassard, a professor at the Université de Montréal, continues to work on quantum cryptography and quantum communication. Bennett, now retired from IBM, remains an active figure in the field.
The 2025 Turing Award does not close a chapter. It marks how far the field has come — and how much of that distance was covered by two people who, in 1984, published a paper most people ignored.
