We explore the possibility of detecting entangled photon pairs from two patches of the sky, such as cosmic microwave background or other cosmological sources. The measurements use two detectors with different photon polarizer directions. When two photon sources are separated by a large angle, a null test of unentangled photons can be performed. The deviation from this unentangled background is the signature of photon entanglement. To confirm whether the deviation is consistent with entangled photons, we derive the photon polarization correlation to compare with, similar to that in a Bell inequality measurement. Besides, with the use of holographic Schwinger–Keldysh correlators, we construct the CHSH (Clauser–Horne–Shimony–Holt) form of Bell inequality, and find that its violation can also be implemented in the holographic model of EPR (Einstein–Podolsky–Rosen) pair.　　

个人简介：张云龙，中科院国家天文台副研究员。2014年中科院理论物理所获理学博士，先后在台湾大学、韩国亚太理论物理中心APCTP进行博士后研究。2018年起任日本京都大学JSPS学者、Yukawa基础物理研究所特任助理教授，2020年底入职中科院国家天文台。研究领域为引力理论和宇宙学，包括黑洞物理和引力全息应用、超轻暗物质和引力波探测等。 

Contact联系人 王少江