Verification of continuous variable entanglement with undetected photons

TL;DR

This paper demonstrates a novel method to verify continuous variable entanglement of photon pairs without coincidence detection, using a nonlinear interferometric technique that is robust to losses and applicable to high-dimensional entanglement.

Contribution

It introduces a new approach for entanglement verification that does not require detecting both photons, enabling applications in scenarios with detector limitations and high-dimensional quantum states.

Findings

Successfully violated EPR and MGVT criteria using single-photon interference

Method remains effective under experimental losses

Applicable to highly non-degenerate and high-dimensional entanglement

Abstract

We verify transverse spatial entanglement of photon-pairs generated in spontaneous parametric down conversion using a nonlinear interferometric technique without relying on any coincidence detection. We experimentally demonstrate the violation of the Einstein-Podolsky-Rosen criterion and of the Mancini-Giovannetti-Vitali-Tombesi criterion using single photon interference of one of the photons of the pairs. We also provide a comprehensive theoretical analysis. The experimental results that we have obtained show good agreement with the theoretical values. Our method performs well under experimental losses and can be applied to highly non-degenerate sources, where there are no suitable detectors for one of the photons in the quantum state and our method could also be extended to the discrete degrees of freedom to certify high-dimensional (OAM) entanglement.