High-fidelity entanglement swapping with fully independent sources

TL;DR

This paper demonstrates high-fidelity entanglement swapping using fully independent, time-synchronized sources, enabling robust quantum communication and foundational tests by violating Bell inequalities.

Contribution

It presents the first demonstration of entanglement swapping with fully independent sources achieving a Bell inequality violation, suitable for long-distance quantum networks.

Findings

Achieved entanglement swapping with independent sources.

Fidelity high enough to violate Bell inequality by over four standard deviations.

Suitable for future quantum communication and foundational physics tests.

Abstract

Entanglement swapping allows to establish entanglement between independent particles that never interacted nor share any common past. This feature makes it an integral constituent of quantum repeaters. Here, we demonstrate entanglement swapping with time-synchronized independent sources with a fidelity high enough to violate a Clauser-Horne-Shimony-Holt inequality by more than four standard deviations. The fact that both entangled pairs are created by fully independent, only electronically connected sources ensures that this technique is suitable for future long-distance quantum communication experiments as well as for novel tests on the foundations of quantum physics.