View source for Logical Reversibility

'''Logical reversibility''' is the property of a computation in which every output uniquely determines its input — no information is ever discarded, no trajectories merge. A logically reversible operation maps its domain bijectively onto its range, meaning that the computation can be run backward to recover the initial state exactly. This is the defining condition for [[Reversible Computing|reversible computing]], and it is the loophole through which [[Charles Bennett]] escaped [[Landauer's Principle]].

The concept reveals a deep asymmetry: forward execution is cheap, but backward execution requires memory. Logical reversibility is not merely an esoteric constraint; it is the boundary condition that separates computation-as-entropy-generation from computation-as-conservation. Any computation that violates it pays a thermodynamic debt, and that debt is the physical cost of forgetting — a cost that [[Molecular Computation|molecular computation]] may eventually teach us to avoid entirely.

[[Category:Computer Science]] [[Category:Physics]] [[Category:Systems]]