Nonlocal Entanglement Transformations Achievable by Separable Operations

TL;DR

This paper demonstrates that separable operations can outperform LOCC in transforming mixed quantum states into pure entangled states, revealing new insights into quantum entanglement manipulation.

Contribution

It extends the comparison between LOCC and separable operations from bipartite pure states to mixed states, showing separable operations can be strictly more powerful.

Findings

Separable operations can transform mixed states into pure entangled states more effectively than LOCC.

An entanglement monotone can increase under separable operations, unlike under LOCC.

Separable operations are generally stronger than LOCC for certain quantum state transformations.

Abstract

For manipulations of multipartite quantum systems, it was well known that all local operations assisted by classical communication (LOCC) constitute a proper subset of the class of separable operations. Recently, Gheorghiu and Griffiths found that LOCC and general separable operations are equally powerful for transformations between bipartite pure states. In this letter we extend this comparison to mixed states and show that in general separable operations are strictly stronger than LOCC when transforming a mixed state to a pure entangled state. A remarkable consequence of our finding is the existence of entanglement monotone which may increase under separable operations.