  The microscopic state space of the system and environment is assumed to be divided into logical, or information bearing, degrees of freedom and environmental, or non-information bearing degrees of freedom. These can be simplified to just two dimensions. In the figure, the horizontal axis represents the information bearing degrees of freedom. The system being in logical state zero or logical state one corresponds to the microscopic state lying within a particular region of the information bearing degree of freedom. The reset to zero operation is required to be a Hamiltonian evolution of the state space of the system and environment that leaves the system in logical state zero, regardless of the initial logical state.