  As logically reversible operations need to be 1:1 maps, Landauer argued they can be implemented by physical devices which do not compress the physical state space. Logically irreversible operations reduce the logical state space, so must compress the physical state space. Landauer argued that this must be accompanied by a corresponding entropy increase in the environment, in the form of heat dissipation. Most familiar logical operations are irreversible and so by this argument must generate heat.