On the Structure of Postselective Transformations of Quantum States

We study the properties of postselective transformations of quantum states, that is, transformations for which some classical results are declared “successful” while the rest are discarded. We demonstrate that for every postselective transformation there exists a distinguished orthonormal basis for which the transformation reduces to probabilistic blocking of the basis states followed by a deterministic transformation. We also describe a generalization of an arbitrary postselective transformation that corresponds to its partial version with a given success probability.