title: Demonstration of local expansion toward large-scale entangled webs.
abstract: We demonstrate an optical gate that increases the size of polarization-based W states by accessing only one of the qubits. Using this gate, we have generated three-photon and four-photon W states with fidelities 0.836 ± 0.042 and 0.784 ± 0.028, respectively. We also confirmed the existence of pairwise entanglement in every pair of qubits, including the one that was left untouched by the gate. The gate is applicable to any size of W states and hence is a universal tool for expanding entanglement.
authors.affiliation: Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Tashima
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Kitano
authors.forename: Sahin Kaya
authors.initials: SK
authors.lastname: Ozdemir
authors.forename: Takashi
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Masato
authors.initials: M
authors.lastname: Koashi
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Imoto