title: Generation of large-amplitude coherent-state superposition via ancilla-assisted photon subtraction.
abstract: We propose and demonstrate a novel method to generate a large-amplitude coherent-state superposition (CSS) via ancilla-assisted photon subtraction. The ancillary mode induces quantum interference of indistinguishable processes in an extended space, widening the controllability of quantum superposition at the conditional output. We demonstrate this by a simple time-separated two-photon subtraction from continuous wave squeezed light. We observe the largest CSS of traveling light ever reported without correcting any imperfections, which will enable various quantum information applications with CSS states.
authors.affiliation: National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei, Tokyo 184-8795, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Takahashi
authors.forename: Kentaro
authors.initials: K
authors.lastname: Wakui
authors.forename: Shigenari
authors.initials: S
authors.lastname: Suzuki
authors.forename: Masahiro
authors.initials: M
authors.lastname: Takeoka
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Hayasaka
authors.forename: Akira
authors.initials: A
authors.lastname: Furusawa
authors.forename: Masahide
authors.initials: M
authors.lastname: Sasaki