Scientific Results

Not all pure entangled states are useful for sub-shot-noise interferometry

Year: 2010

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. [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

Citations: 67
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