Ultrafine Entanglement Witnessing

TL;DR

This paper introduces an improved entanglement detection method that enhances standard witnesses by utilizing extra information, simplifying implementation, and scaling efficiently to complex quantum systems.

Contribution

It presents a novel, easy-to-implement entanglement witnessing procedure that tightens bounds without complex decompositions, applicable to higher-dimensional and multipartite systems.

Findings

Successfully demonstrated entanglement detection experimentally

Method improves detection efficiency and robustness

Scales linearly with the number of parties in multipartite systems

Abstract

Entanglement witnesses are invaluable for efficient quantum entanglement certification without the need for expensive quantum state tomography. Yet, standard entanglement witnessing requires multiple measurements and its bounds can be elusive as a result of experimental imperfections. Here we introduce and demonstrate a novel procedure for entanglement detection which seamlessly and easily improves any standard witnessing procedure by using additional available information to tighten the witnessing bounds. Moreover, by relaxing the requirements on the witness operators, our method removes the general need for the difficult task of witness decomposition into local observables. We experimentally demonstrate entanglement detection with our approach using a separable test operator and a simple fixed measurement-device for each agent. Finally we show that the method can be generalized to higher-dimensional and multipartite cases with a complexity that scales linearly with the number of parties.