Rolf Landauer

Rolf Landauer was born in Stuttgart in 1927 and fled Nazi Germany with his family in 1938, settling in the United States. He earned his PhD from Harvard and in 1952 joined IBM, where he spent his career and became one of the foundational figures in the physics of computation.

In 1961 Landauer established the principle that bears his name: that erasing one bit of information must dissipate at least k_BT ln 2 of energy as heat, because erasure is the one logically irreversible operation. This identified the unavoidable thermodynamic cost of computation and located it precisely in the destruction, not the processing, of information.

Landauer's broader message, captured in his slogan 'information is physical', was that information is never abstract but always tied to a physical carrier subject to the laws of thermodynamics. The insight reshaped how physicists think about computation and underlies the modern fields of reversible and quantum computing.

He also made fundamental contributions to mesoscopic physics, including the Landauer formula relating electrical conductance to quantum transmission probabilities. He remained scientifically active at IBM until shortly before his death in 1999.