Abstract : We show that the quantum Fisher information provides a sufficient condition to recognize multi-particle entanglement in a N qubit state. The same criterion gives a necessary and sufficient condition for sub shot-noise phase sensitivity in the estimation of a collective rotation angle θ . The analysis therefore singles out the class of entangled states which are {\it useful} to overcome classical phase sensitivity in metrology and sensors. We finally study the creation of useful entangled states by the non-linear dynamical evolution of two decoupled Bose-Einstein condensates or trapped ions.
https://hal-iogs.archives-ouvertes.fr/hal-00626569 Contributor : Marie-Laure EdwardsConnect in order to contact the contributor Submitted on : Thursday, March 31, 2016 - 4:23:19 PM Last modification on : Wednesday, October 14, 2020 - 3:59:49 AM Long-term archiving on: : Monday, November 14, 2016 - 11:35:48 AM