Charles H. Bennett (physicist)

Charles Henry Bennett (born 1943) is an American physicist, information theorist and IBM Fellow at IBM Research. Bennett's recent work at IBM has concentrated on a re-examination of the physical basis of information, applying quantum physics to the problems surrounding information exchange. He has played a major role in elucidating the interconnections between physics and information, particularly in the realm of quantum computation, but also in cellular automata and reversible computing.

He co-developed the first practical quantum cryptography protocol (BB84) with Gilles Brassard and is one of the founding fathers of modern quantum information theory (see Bennett's four laws of quantum information). He shared the 2025 Turing Award with Brassard for their work in quantum information science.

Early career

Born in 1943 in New York City, Bennett earned a BS in chemistry from Brandeis University in 1964 and received his PhD from Harvard in 1970 for molecular-dynamics studies (computer simulation of molecular motion) under David Turnbull and Berni Alder. At Harvard, he also worked for James Watson one year as a teaching assistant about the genetic code. For the next two years he continued this research under Aneesur Rahman at Argonne National Laboratory (operated by the University of Chicago).

After joining IBM Research in 1972, he built on the work of IBM's Rolf Landauer to show that general-purpose computation can be performed by a logically and thermodynamically reversible apparatus; and in 1982 he proposed a re-interpretation of Maxwell's demon, attributing its inability to break the second law to the thermodynamic cost of destroying, rather than acquiring, information. He also published an important paper on the estimation of free-energy differences between two systems, the Bennett acceptance ratio method.