title: Observation of quantum recoherence of photons by spatial propagation.
abstract: Entanglement is at the heart of many unusual and counterintuitive features of quantum mechanics. Once two quantum subsystems have become entangled, it is no longer possible to ascribe an independent state to either; instead, the subsystems are completely described only as part of a greater, composite system. As a consequence of this, each entangled subsystem experiences a loss of coherence following entanglement. We refer to this decrease in coherence as decoherence. Decoherence leads inevitably to the leaking of information from each subsystem to the composite entangled system. Here, we demonstrate a process of decoherence reversal, whereby we recover information lost from the entanglement of the optical orbital angular momentum and radial profile degrees of freedom possessed by a photon pair. These results carry great potential significance, since quantum memories and quantum communication schemes depend on an experimenter's ability to retain the coherent properties of a particular quantum system.
authors.affiliation: Department of Physics, University of Ottawa, 25 Templeton St., Ottawa, Ontario, K1N 6N5 Canada.
authors.forename: Frédéric
authors.initials: F
authors.lastname: Bouchard
authors.affiliation: Department of Physics, University of Ottawa, 25 Templeton St., Ottawa, Ontario, K1N 6N5 Canada.
authors.forename: Jérémie
authors.initials: J
authors.lastname: Harris
authors.affiliation: Department of Physics, University of Ottawa, 25 Templeton St., Ottawa, Ontario, K1N 6N5 Canada.
authors.forename: Harjaspreet
authors.initials: H
authors.lastname: Mand
authors.affiliation: Department of Physics, University of Ottawa, 25 Templeton St., Ottawa, Ontario, K1N 6N5 Canada.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Bent
authors.affiliation: Dipartimento di Scienze Fisiche, Universitá di Napoli "Federico II", Complesso di Monte S. Angelo, 80126 Napoli, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Santamato
authors.affiliation: Department of Physics, University of Ottawa, 25 Templeton St., Ottawa, Ontario, K1N 6N5 Canada.|Institute of Optics, University of Rochester, Rochester, New York, 14627, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Boyd
authors.affiliation: Department of Physics, University of Ottawa, 25 Templeton St., Ottawa, Ontario, K1N 6N5 Canada.
authors.forename: Ebrahim
authors.initials: E
authors.lastname: Karimi