Charles Bennett honoured for reversible computation
Charles H. Bennett, who in 1973 proved that computation can in principle be carried out reversibly, has received the 2025 ACM A.M. Turing Award. The award — shared, and recognising largely his work in quantum information and the physics of computation — honours a body of work that founded the field of reversible computing.
The 1973 result
Bennett's "Logical Reversibility of Computation" answered a question that had hung over the new physics of information. Landauer had shown in 1961 that erasing a bit must release heat; the worry was that real computation seemed to erase constantly, so this thermodynamic toll looked unavoidable. Bennett showed it was not. Any computation, he proved, can be rearranged so that no information is ever discarded: the machine runs forward, copies out its answer, then runs backward to uncompute every intermediate result, leaving its scratch memory clean and the energy debt unpaid.
That construction is the cornerstone of reversible and zero-energy computing. It separates the logical question — can we compute without forgetting? — from the engineering one, and answers the logical question with a clear yes. Everything that has followed, from reversible programming languages to adiabatic energy-recovery hardware, builds on it.
A career in the physics of information
The Turing Award recognises far more than the 1973 paper. Over a long career Bennett helped establish the thermodynamics of computation, co-invented quantum key distribution and quantum teleportation, and did much to make "the physics of information" a discipline in its own right. In our words, this is an award for that whole body of work rather than for reversible computation alone — but reversible computation is one of its load-bearing pillars, and the recognition lands squarely in our field.
For the Institute, the citation is a welcome marker: the ideas that motivate near-zero-energy programming are not fringe speculation but foundational computer science, now honoured at the discipline's highest level. Readers can find more in Bennett's biography.
Source: Bennett, C. H. (1973), "Logical Reversibility of Computation", IBM J. R&D; biography at Wikipedia.