Spatial EPR entanglement in atomic vapor quantum memory

Spatially-structured quantum states of light are staring to play a key role in modern quantum science with the rapid development of single-photon sensitive cameras [1]. In particular, spatial degree of freedom holds a promise to enhance continous-variable quantum memories. Here we present the first demonstration of spatial entanglement between an atomic spin-wave and a photon [2] measured with an I-sCMOS camera. The system is realized in a warm atomic vapor quantum memory based on rubidium atoms immersed in inert buffer gas. In the experiment we create and characterize a 12-dimensional entangled state exhibiting quantum correlations between a photon and an atomic ensemble in position and momentum bases. This state allows us to demonstrate the Einstein-Podolsky-Rosen paradox in its original version [3], with an unprecedented delay time of 6 $\mu$s between generation of entanglement and detection of the atomic state.\newline \newline [1] R. Chrapkiewicz, M. Jachura, K. Banaszek, and W.Wasilewski, Nat. Photonics 10, 576 (2016).\newline [2] M. D\k{a}browski, M. Parniak and W. Wasilewski, "Einstein-Podolsky-Rosen Paradox in a Hybrid Bipartite System", arXiv:1607.05865 \newline [3] A. Einstein, B. Podolsky, and N. Rosen, Phys. Rev. 47, 777 (1935)