title: Quantum metrology assisted by abstention.
abstract: The main goal of quantum metrology is to obtain accurate values of physical parameters using quantum probes. In this context, we show that abstention, i.e., the possibility of getting an inconclusive answer at readout, can drastically improve the measurement precision and even lead to a change in its asymptotic behavior, from the shot-noise to the Heisenberg scaling. We focus on phase estimation and quantify the required amount of abstention for a given precision. We also develop analytical tools to obtain the asymptotic behavior of the precision and required rate of abstention for arbitrary pure states.
authors.affiliation: Física Teòrica: Informació i Fenòmens Quàntics, Departament de Física, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain.
authors.forename: B
authors.initials: B
authors.lastname: Gendra
authors.forename: E
authors.initials: E
authors.lastname: Ronco-Bonvehi
authors.forename: J
authors.initials: J
authors.lastname: Calsamiglia
authors.forename: R
authors.initials: R
authors.lastname: Muñoz-Tapia
authors.forename: E
authors.initials: E
authors.lastname: Bagan