Various quantum nonlocality tests with a simple 2-photon entanglement source

TL;DR

This paper demonstrates various quantum nonlocality tests using a simple 2-photon entangled source, including multiple Bell inequalities, showing violations and quantifying generated randomness, thus deepening understanding of quantum nonlocality.

Contribution

It experimentally implements and compares multiple nonlocality tests with a common entangled photon source, highlighting advantages of complex inequalities over CHSH.

Findings

Violation of I3322, I4422, and chained inequalities.

Upper limit of 0.49 on local content with chained inequality.

Quantification of true randomness generated in the experiment.

Abstract

Nonlocality is a fascinating and counterintuitive aspect of Nature, revealed by the violation of a Bell inequality. The standard and easiest configuration in which Bell inequalities can be measured has been proposed by Clauser-Horne-Shimony-Holt (CHSH). However, alternative nonlocality tests can also be carried out. In particular, Bell inequalities requiring multiple measurement settings can provide deeper fundamental insights about quantum nonlocality as well as offering advantages in the presence of noise and detection inefficiency. In this article we show how these nonlocality tests can be performed using a commercially available source of entangled photon pairs. We report the violation of a series of these nonlocality tests (I3322, I4422 and chained inequalities). With the violation of the chained inequality with 4 settings per side we put an upper limit at 0.49 on the local content of the states prepared by the source (instead of 0.63 attainable with CHSH). We also quantify the amount of true randomness that has been created during our experiment (assuming fair sampling of the detected events).