Indistinguishability of Independent Two Entangled Photon Pairs from Warm Atomic Ensembles using a Quantum Eraser-Like Interferometer

Indistinguishability between mutually independent quantum light sources is a fundamental requirement for various quantum information protocols. In this study, we experimentally evaluate the indistinguishability of independent twin entangled photon pairs generated from ⁸⁷Rb atomic ensembles using a quantum eraser-like interferometer scheme. We mixed two independent entangled photon pairs generated via spontaneous four-wave mixing (SFWM) at a beam splitter to erase path information. Using this setup, we observed interference fringes with a high visibility exceeding 98% that confirms the high indistinguishability between the independent photon pairs. We also investigated how distinguishability arising from path information in polarization and path loss reduces the interference visibility. Moreover, we analyzed the coherence properties between the two independent heralded photon pairs by varying the optical path length difference. Based on these results, we propose the employed interferometer scheme as an effective tool for testing the indistinguishability of independent entangled photon pairs.