All Q-operations

Abstract

So far we have learned certain particular q-operations like the unitary transformations, the q-measurements, and the reduction of state. The set of generic q-operations is much larger. We learn the elegant mathematical classification. We discuss its various physical interpretations typically involving the temporary enlargement of the system by a certain environmental system, subsequent unitary and measurement operations on the obtained composite system, and an ultimate reduction to the original system. © 2011 Springer-Verlag Berlin Heidelberg.