title: Einstein-Podolsky-Rosen Entanglement of Narrow-Band Photons from Cold Atoms.
abstract: Einstein-Podolsky-Rosen (EPR) entanglement introduced in 1935 deals with two particles that are entangled in their positions and momenta. Here we report the first experimental demonstration of EPR position-momentum entanglement of narrow-band photon pairs generated from cold atoms. By using two-photon quantum ghost imaging and ghost interference, we demonstrate explicitly that the narrow-band photon pairs violate the separability criterion, confirming EPR entanglement. We further demonstrate continuous variable EPR steering for positions and momenta of the two photons. Our new source of EPR-entangled narrow-band photons is expected to play an essential role in spatially multiplexed quantum information processing, such as, storage of quantum correlated images, quantum interface involving hyperentangled photons, etc.
authors.affiliation: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea.
authors.forename: Jong-Chan
authors.initials: JC
authors.lastname: Lee
authors.affiliation: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea.
authors.forename: Kwang-Kyoon
authors.initials: KK
authors.lastname: Park
authors.affiliation: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea.
authors.forename: Tian-Ming
authors.initials: TM
authors.lastname: Zhao
authors.affiliation: Department of Physics, Pohang University of Science and Technology (POSTECH), Pohang 37673, Korea.
authors.forename: Yoon-Ho
authors.initials: YH
authors.lastname: Kim