Entanglement estimation in non-optimal qubit states
Authors: Scali S., Franzosi R.
Autors Affiliation: DSFTA, University of Siena, Via Roma 56, 53100 Siena, Italy; Department of Physics, University of Cambridge, Cambridge CB3 0HE, United Kingdom; Department of Physics and Astronomy, University of Exeter, Exeter EX4 4QL, United Kingdom; STAR & CNR – Istituto Nazionale di Ottica, Largo Enrico Fermi 2, I-50125 Firenze, ItalyFirenze, Italy, Italy
Abstract: In the case of two qubits, all pure entangled states can be made useful for sub-shot-noise interfer- ometry . However, with non-optimal two-qubit states, the value of quantum Fisher information provides just a sufficient condition in the task of detecting the degree of entanglement of a generic state. We show analytically that for a large class of one-parameter non-optimal two-qubit states, the maximally entangled states are associated with stationary points of the quantum Fisher infor- mation, as a function of such parameter. We show, via numerical simulations, that this scenario is maintained for the generalization of this class of states to a generic M-qubits system. Furthermore, we suggest a scheme for an interferometer able to detect the entanglement in a large class of two-spin states.
Journal/Review: ANNALS OF PHYSICS
Volume: 411 Pages from: 167995-1 to: 167995-11
KeyWords: Quantum InformationDOI: 10.1016/j.aop.2019.167995Citations: 1data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2021-10-24References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here