Not all pure entangled states are useful for sub-shot-noise interferometry
Year: 2010
Authors: Hyllus P., G�hne O., Smerzi A.
Autors Affiliation: BEC-CNR-INFM and Dipartimento di Fisica, Universit� di Trento, I-38050 Povo, Italy; Institut f�r Quantenoptik und Quanteninformation, �sterreichische Akademie der Wissenschaften, Technikerstra�e 21A, A-6020 Innsbruck, Austria; Institut f�r Theoretische Physik, Universit�t Innsbruck, Technikerstra�e 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. [70] to us. O.G. acknowledges support by the FWF (START program and SFB FoQuS) and the EU (NAMEQUAM, QICS, SCALA).
DOI: 10.1103/PhysRevA.82.012337
ImpactFactor: 2.861
Citations: 108
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