Two-qubit catalysis in a four-state pure bipartite system

TL;DR

This paper investigates how two-qubit catalysts can enable state transformations in a four-qubit bipartite system that are otherwise impossible with LOCC, providing a complete criterion for such catalysis.

Contribution

It introduces a necessary and sufficient condition for two-qubit catalysis in pure bipartite systems, expanding understanding of quantum state transformations.

Findings

Identifies when two-qubit catalysts enable transformations

Provides a complete criterion for catalysis in four-state systems

Enhances the understanding of LOCC limitations

Abstract

We consider a four-state pure bipartite system consisting of four qubits shared among two parties using the same Schmidt basis, two qubits per party. In some cases, transformation between two known pure states may not be possible using LOCC transformations but may be possible with the addition of a two-qubit catalyst. We provide a necessary and sufficient condition for this to occur.