Not all pure entangled states are useful for sub-shot-noise interferometry
Authors: Hyllus P., Gühne O., Smerzi A.
Autors Affiliation: BEC-CNR-INFM and Dipartimento di Fisica, Università di Trento, I-38050 Povo, Italy; Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, Technikerstraße 21A, A-6020 Innsbruck, Austria; Institut für Theoretische Physik, Universität Innsbruck, Technikerstraße 25, A-6020 Innsbruck, Austria
Abstract: We investigate the connection between the shot-noise limit in linear interferometers and particle entanglement. In particular, we ask whether sub-shot-noise sensitivity can be reached with all pure entangled input states of N particles if they can be optimized with local operations. Results on the optimal local transformations allow us to show that for N = 2 all pure entangled states can be made useful for sub-shot-noise interferometry while for N > 2 this is not the case. We completely classify the useful entangled states available in a bosonic two-mode interferometer. We apply our results to several states, in particular to multiparticle singlet states and to cluster states. The latter turn out to be practically useless for sub-shot-noise interferometry. Our results are based on the Cramer-Rao bound and the Fisher information.
Journal/Review: PHYSICAL REVIEW A
Volume: 82 (1) Pages from: 012337 to: 012337
More Information: We thank J. I. Cirac for fruitful discussions and G. Toth for pointing out Ref.  to us. O.G. acknowledges support by the FWF (START program and SFB FoQuS) and the EU (NAMEQUAM, QICS, SCALA).DOI: 10.1103/PhysRevA.82.012337Citations: 67data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2019-10-13References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here