title: Filtering out photonic Fock states.
abstract: Unprecedented optical nonlinearities can be generated probabilistically in simple linear-optical networks conditioned on specific measurement outcomes. We describe a highly controllable quantum filter for photon number states, which takes advantage of such a measurement-induced amplitude nonlinearity. The basis for this filter is multiphoton nonclassical interference which we demonstrate for one- and two-photon states over a wide range of beam splitter reflectivities. Specifically, we show that the transmission probability, conditional on a specific measurement outcome, can be larger for a two-photon state than a one-photon state; this is not possible with linear optics alone.
authors.affiliation: Institut für Experimentalphysik, Universität Wien, Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Kaoru
authors.initials: K
authors.lastname: Sanaka
authors.forename: Kevin J
authors.initials: KJ
authors.lastname: Resch
authors.forename: Anton
authors.initials: A
authors.lastname: Zeilinger