Charles Bennett

Charles H. Bennett, born in 1943, is an American physicist and information theorist who has spent much of his career at IBM Research. In 1973 he showed that computation can in principle be made logically reversible, and therefore performed with arbitrarily little energy dissipation — a result that sharpened Landauer's principle by isolating erasure as the sole source of unavoidable cost.

In 1982 Bennett used this insight to give the definitive resolution of the Maxwell's-demon paradox. He argued that the demon's memory is finite and must eventually be erased to continue operating, and that this erasure dissipates exactly the energy the demon appears to gain. The entropy the demon seemed to destroy is paid back in full when it forgets.

Bennett went on to become one of the founders of quantum information science. With Gilles Brassard he invented quantum cryptography in 1984 (the BB84 protocol), and in 1993 he led the team that discovered quantum teleportation. These results made him one of the most influential figures in the modern understanding of information as a physical resource.

His work threads together thermodynamics, computation and quantum mechanics, showing repeatedly that the abstract notion of information is governed by physical law.