title: Optimal scheme for estimating a pure qubit state via local measurements.
abstract: We present the optimal scheme for estimating a pure qubit state by means of local measurements on N identical copies. We give explicit examples for low N. For large N, we show that the fidelity saturates the collective measurement bound up to order 1/N. When the signal state lays on a meridian of the Bloch sphere, we show that this can be achieved without classical communication.
authors.affiliation: Grup de Física Teòrica & IFAE, Facultat de Ciències, Edifici Cn, Universitat Autònoma de Barcelona, 08193 Bellaterra (Barcelona), Spain.
authors.forename: E
authors.initials: E
authors.lastname: Bagan
authors.forename: M
authors.initials: M
authors.lastname: Baig
authors.forename: R
authors.initials: R
authors.lastname: Muñoz-Tapia