Witness based nonlinear detection of quantum entanglement

TL;DR

This paper introduces a nonlinear entanglement detection method that surpasses linear strategies, capable of identifying entanglement with multiple copies and applicable to multipartite systems and entanglement concentration.

Contribution

The authors propose a novel nonlinear detection strategy that improves entanglement detection capabilities beyond traditional linear methods, including multipartite and concentration scenarios.

Findings

Nonlinear detection succeeds where linear fails with two copies.

Detection improves with three or more copies.

Method applies to multipartite entanglement and entanglement concentration.

Abstract

We present a nonlinear entanglement detection strategy which detects entanglement that the linear detection strategy fails. We show that when the nonlinear entanglement detection strategy fails to detect the entanglement of an entangled state with two copies, it may succeed with three or more copies. Based on our strategy, a witness combined with a suitable quanutm mechanical observable may detect the entanglement that can not be detected by the witness alone. Moreover, our strategy can also be applied to detect multipartite entanglement by using the witnesses for bipartite systems, as well as to entanglement concentrations.