title: Experimental bound entanglement in a four-photon state.
abstract: Bound entanglement is central to many exciting theoretical results in quantum information processing, but has thus far not been experimentally realized. In this work, we consider a one-parameter family of four-qubit Smolin states. We experimentally produce these states in the polarization of four optical photons produced from parametric down-conversion. Within a range of the parameter, we show that our states are entangled and undistillable, and thus bound entangled. Using these bound-entangled states we demonstrate entanglement unlocking.
authors.affiliation: Institute for Quantum Computing and Department of Physics and Astronomy, University of Waterloo, Waterloo, Canada.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Lavoie
authors.forename: Rainer
authors.initials: R
authors.lastname: Kaltenbaek
authors.forename: Marco
authors.initials: M
authors.lastname: Piani
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Resch