Device-independent demonstration of genuine multipartite entanglement

TL;DR

This paper experimentally demonstrates device-independent witnesses for genuine multipartite entanglement and quantum nonlocality in a system of up to six ions, avoiding measurement device assumptions.

Contribution

It provides the first experimental validation of device-independent entanglement witnesses for multipartite systems with up to six particles.

Findings

Successful detection of genuine multipartite entanglement in six ions.

Observation of quantum nonlocality with detection loophole closed.

Validation of device-independent approach in practical quantum systems.

Abstract

Entanglement in a quantum system can be demonstrated experimentally by performing the measurements prescribed by an appropriate entanglement witness. However, the unavoidable mismatch between the implementation of measurements in practical devices and their precise theoretical modelling generally results in the undesired possibility of false-positive entanglement detection. Such scenarios can be avoided by using the recently developed device-independent entanglement witnesses (DIEWs) for genuine multipartite entanglement. Similarly to Bell inequalities, DIEWs only assume that consistent measurements are performed locally on each subsystem. No precise description of the measurement devices is required. Here we report an experimental test of DIEWs on up to six entangled 40Ca+ ions. We also demonstrate genuine multipartite quantum nonlocality between up to six parties with the detection loophole closed.