Deterministic Local Conversion of Incomparable States by Collective LOCC

Abstract

Incomparability of pure bipartite entangled states under deterministic LOCC is a very strange phenomena. We find two possible ways of getting our desired pure entangled state which is incomparable with the given input state, by collective LOCC with certainty. The first one is by providing some pure entanglement through the lower dimensional maximally-entangled states or using further less amount of entanglement and the next one is by collective operation on two pairs which are individually incomparable. It is quite surprising that we are able to achieve maximally entangled states of any Schmidt rank from a finite number of $2\times 2$ pure entangled states only by deterministic LOCC. We provide general theory for the case of $3\times3$ system of incomparable states by the above processes where incomparability seems to be the most hardest one.