Ancilla bitIn reversible computing, ancilla bits are extra bits being used to implement irreversible logical operations. In classical computation, any memory bit can be turned on or off at will, requiring no prior knowledge or extra complexity. However, this is not the case in quantum computing or classical reversible computing. In these models of computing, all operations on computer memory must be reversible, and toggling a bit on or off would lose the information about the initial value of that bit.
Two-state quantum systemIn quantum mechanics, a two-state system (also known as a two-level system) is a quantum system that can exist in any quantum superposition of two independent (physically distinguishable) quantum states. The Hilbert space describing such a system is two-dimensional. Therefore, a complete basis spanning the space will consist of two independent states. Any two-state system can also be seen as a qubit. Two-state systems are the simplest quantum systems that are of interest, since the dynamics of a one-state system is trivial (as there are no other states the system can exist in).
Calcul réversibleLe calcul réversible est un domaine de l'informatique qui s'intéresse au fait de pouvoir inverser (physiquement ou logiquement) un calcul. Il s'agit d'un domaine transversal, qui a des applications allant de l'architecture matérielle à l'algorithmique répartie en passant par le calcul quantique. D'un point de vue physique, cela implique que ce calcul n'implique pas de phénomène dissipatif conduisant à une augmentation de l'entropie ; bien qu'il soit physiquement impossible d'atteindre cet objectif du fait du second principe de la thermodynamique, s'en rapprocher permet l'augmentation de l'efficacité des processeurs.
