Experimental self-testing of entangled states

TL;DR

This paper experimentally demonstrates a complete self-testing process for bipartite entangled states up to four dimensions, certifying their form with over 99.9% fidelity using measurement correlations, advancing practical quantum certification.

Contribution

It introduces a robust, complete self-testing method for high-dimensional bipartite entangled states, surpassing previous rough estimations and enabling practical quantum state certification.

Findings

Achieved over 99.9% fidelity in certifying entangled states

Successfully self-tested states up to four dimensions

Demonstrated robustness and completeness of the method

Abstract

Quantum entanglement is the key resource for quantum information processing. Device-independent certification of entangled states is a long standing open question, which arouses the concept of self-testing. The central aim of self-testing is to certify the state and measurements of quantum systems without any knowledge of their inner workings, even when the used devices cannot be trusted. Specifically, utilizing Bell's theorem, it is possible to place a boundary on the singlet fidelity of entangled qubits. Here, beyond this rough estimation, we experimentally demonstrate a complete self-testing process for various pure bipartite entangled states up to four dimensions, by simply inspecting the correlations of the measurement outcomes. We show that this self-testing process can certify the exact form of entangled states with fidelities higher than 99.9% for all the investigated scenarios, which indicates the superior completeness and robustness of this method. Our work promotes self-testing as a practical tool for developing quantum techniques.