Quantum Discord Determines the Interferometric Power of Quantum States

By Davide Girolami, A. M. Souza, Vittorio Giovannetti, T. Tufarelli, J. G. Filgueiras, R. Sarthour, D. Soares-Pinto, I. S. Oliveira, Gerardo Adesso. 2013

198 citations recorded by the source corpus.

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.

Subfields: Artificial Intelligence, Atomic and Molecular Physics, and Optics

View Paper: https://www.semanticscholar.org/paper/5aa6a974e6614a8c7eb3475b26da8ec209a0e181

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Citations in the corpus

Quantum-enhanced measurements without entanglement (2017, methodology): “An experimental demonstration of black-box quantum-enhanced measurements relying on discordant states as opposed to classically correlated states has been reported using a two-qubit NMR ensemble realized in chloroform (Girolami et al., 2014).”
Quantum information processing with superconducting circuits: a review (2016, background): “Quantum discord deter mines the interferometric power of quantum states [104].”