Quantum discord determines the interferometric power of quantum states

Girolami, Davide and Souza, Alexandre M. and Giovannetti, Vittorio and Tufarelli, Tommaso and Filgueiras, Jefferson G. and Sarthour, Roberto S. and Soares-Pinto, Diogo O. and Oliveira, Ivan S. and Adesso, Gerardo (2014) Quantum discord determines the interferometric power of quantum states. Physical Review Letters, 112 (21). 210401-1-210401-5. ISSN 1079-7114

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Quantum metrology exploits quantum mechanical laws to improve the precision in estimating technologically relevant parameters such as phase, frequency, or magnetic fields. Probe states are usually tailored to the particular dynamics whose parameters are being estimated. Here we consider a novel framework where quantum estimation is performed in an interferometric configuration, using bipartite probe states prepared when only the spectrum of the generating Hamiltonian is known. We introduce a figure of merit for the scheme, given by the worst-case precision over all suitable Hamiltonians, and prove that it amounts exactly to a computable measure of discord-type quantum correlations for the input probe. We complement our theoretical results with a metrology experiment, realized in a highly controllable room-temperature nuclear magnetic resonance setup, which provides a proof-of-concept demonstration for the usefulness of discord in sensing applications. Discordant probes are shown to guarantee a nonzero phase sensitivity for all the chosen generating Hamiltonians, while classically correlated probes are unable to accomplish the estimation in a worst-case setting. This work establishes a rigorous and direct operational interpretation for general quantum correlations, shedding light on their potential for quantum technology.

Item Type: Article
Additional Information: ©2014 American Physical Society
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Mathematical Sciences
Identification Number: 10.1103/PhysRevLett.112.210401
Depositing User: Eprints, Support
Date Deposited: 12 Oct 2017 07:37
Last Modified: 14 Oct 2017 08:27
URI: http://eprints.nottingham.ac.uk/id/eprint/47216

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