title: Experimental implementation of the optimal linear-optical controlled phase gate.
abstract: We report on the first experimental realization of optimal linear-optical controlled phase gates for arbitrary phases. The realized scheme is entirely flexible in that the phase shift can be tuned to any given value. All such controlled phase gates are optimal in the sense that they operate at the maximum possible success probabilities that are achievable within the framework of postselected linear-optical implementations with vacuum ancillas. The quantum gate is implemented by using bulk optical elements and polarization encoding of qubit states. We have experimentally explored the remarkable observation that the optimum success probability is not monotone in the phase.
authors.affiliation: Joint Laboratory of Optics of Palacký University, Institute of Physics of Academy of Sciences of the Czech Republic, 779 07 Olomouc, Czech Republic.
authors.forename: Karel
authors.initials: K
authors.lastname: Lemr
authors.forename: A
authors.initials: A
authors.lastname: Cernoch
authors.forename: J
authors.initials: J
authors.lastname: Soubusta
authors.forename: K
authors.initials: K
authors.lastname: Kieling
authors.forename: J
authors.initials: J
authors.lastname: Eisert
authors.forename: M
authors.initials: M
authors.lastname: Dušek