Robust Self-Testing of Multiparticle Entanglement

TL;DR

This paper presents the first robust self-testing method for multi-photon entangled states, certifying genuine four-photon entanglement using input-output statistics with high fidelity in a device-independent way.

Contribution

It introduces a novel robust self-testing approach for multi-photon entangled states, extending device-independent certification to more complex quantum systems.

Findings

Successfully certified four-photon GHZ states with 95.7% fidelity.

Successfully certified four-photon linear cluster states with 94.5% fidelity.

Demonstrated robustness of self-testing against realistic noise conditions.

Abstract

Quantum self-testing is a device-independent way to certify quantum states and measurements using only the input-output statistics, with minimal assumptions about the quantum devices. Because of the high demand on tolerable noise, however, experimental self-testing was limited to two-photon systems. Here, we demonstrate the first robust self-testing for multi-photon genuinely entangled quantum states. We prepare two examples of four-photon graph states, the Greenberger-Horne-Zeilinger (GHZ) states with a fidelity of 0.957(2) and the linear cluster states with a fidelity of 0.945(2). Based on the observed input-output statistics, we certify the genuine four-photon entanglement and further estimate their qualities with respect to realistic noise in a device-independent manner.