Landauer's principle

Landauer's principle relates logically irreversible information erasure to thermodynamic cost. Resetting an initially equiprobable, uncorrelated one-bit memory to one standard state while coupled to a bath at temperature $T$ requires average heat release of at least $k_{B}T\ln 2$ to the bath in the ideal cyclic setting.

The restriction matters: erasing one unknown bit is different from reversibly transforming a known state, and real devices can dissipate more. The entropy reduction of the memory must be compensated elsewhere. The bound therefore concerns information loss under specified physical conditions, rather than a universal cost for every logic operation.^[ref]

A later experiment represented a bit by the two wells of a potential trapping one colloidal particle. Driving the particle distribution into a chosen well allowed dissipated heat during erasure to be compared with the bound. Approaching the reversible limit requires slow controlled operations; measurement of the work and heat connects the information statement to a physical apparatus.^[ref]