Landauer's principle

Landauer's principle states that logically irreversible operations, such as erasing one bit, require at least kT ln 2 of heat dissipation into an environment at temperature T.

Logical irreversibility: A computation is logically irreversible when its output does not uniquely determine its input. Erasure is the canonical irreversible operation whose physical cost the principle bounds.
Rolf Landauer: A physicist who formulated the connection between logically irreversible computation and heat dissipation. He proposed the principle in 1961 while studying the thermodynamics of information processing.
Reversible logic: A logic system whose gates map each input pattern to a unique output pattern. Reversible gates can avoid erasure during computation, though eventual memory cleanup still has a cost.
Bennett's reversible computation: A method of computing that retains intermediate information so a computation can be reversed without erasing bits. It distinguishes the cost of logically irreversible steps from computation as a whole.
Shannon entropy: A measure of uncertainty in a probability distribution, expressed in bits or other units. The information lost during erasure determines the minimum entropy transferred to the surroundings.
John von Neumann: A mathematician and physicist whose work helped establish the mathematical foundations of quantum mechanics and computing. His discussions of measurement and entropy formed part of the intellectual background to Landauer's argument.
Adiabatic computing: A computing approach that changes circuit states slowly to reduce energy dissipation. It seeks to operate near thermodynamic limits, where Landauer's bound provides a reference.
Margolus–Levitin theorem: A quantum bound relating a system's mean energy to the minimum time required for a state change. It limits computational speed, whereas Landauer's principle limits heat from erasure.
Boltzmann constant: A physical constant relating temperature to energy per unit of entropy. It converts the entropy cost of erasing a bit into an energy scale.
Charles H. Bennett: A physicist who developed reversible computation and clarified the thermodynamic role of information erasure. He showed how reversible computing preserves information until memory must be reset.

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