Abstract
Device-independent certification, also known as self-testing, aims at guaranteeing the proper functioning of untrusted and uncharacterized devices. For example, the quality of an unknown source expected to produce two-qubit maximally entangled states can be evaluated in a bipartite scenario, each party using two binary measurements. The most robust approach consists in deducing the fidelity of produced states with respect to a two-qubit maximally entangled state from the violation of the CHSH inequality. In this paper, we show how the self-testing of two-qubit maximally entangled states is improved by a refined analysis of measurement statistics. The use of suitably chosen Bell tests, depending on the observed correlations, allows one to conclude higher fidelities than ones previously known. In particular, nontrivial self-testing statements can be obtained from correlations that cannot be exploited by a CHSH-based self-testing strategy. Our results not only provide insight into the set of quantum correlations suited for self-testing, but also facilitate the experimental implementations of device-independent certifications.
Highlights
We show how the self-testing of two-qubit maximally entangled states is improved by a refined analysis of measurement statistics
Bell inequalities were proposed to show that the results of local incompatible measurements on subsystems prepared in a global quantum state can have stronger-than-classical correlations, so-called nonlocal correlations [1]
We show that this family of generalized CHSH tests can be used to self-test two-qubit maximally entangled states with a fidelity higher than with the CHSH score whenever X = Y
Summary
Bell inequalities were proposed to show that the results of local incompatible measurements on subsystems prepared in a global quantum state can have stronger-than-classical correlations, so-called nonlocal correlations [1]. A self-test of a two-qubit maximally entangled state φA+B can be obtained from the simplest Bell inequality—the Clauser-Horne-Shimony-Holt (CHSH) inequality [4]. The latter is tested in a bipartite scenario in which Alice and Bob share a state ρAB ∈ HA ⊗ HB and perform one out of two binary measurements each. Note that the case θ = π /4 reduces to the CHSH case We show that this family of generalized CHSH tests can be used to self-test two-qubit maximally entangled states with a fidelity higher than with the CHSH score whenever X = Y. We conclude with an explicit recipe to choose the test giving the highest fidelity in any experiments where the values of correlators X and Y are measured
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
