Nonclassical correlations for quantum metrology in thermal equilibrium

Akira Sone, Quntao Zhuang, Changhao Li, Yi Xiang Liu, Paola Cappellaro

Research output: Contribution to journalArticlepeer-review

11 Scopus citations


Nonclassical correlations beyond entanglement might provide a resource in quantum information tasks, such as quantum computation or quantum metrology. Quantum discord is a measure of nonclassical correlations to which entanglement belongs as a subset. Exploring the operational meaning of quantum discord as a resource in quantum information processing tasks, such as quantum metrology, is of essential importance to our understanding of nonclassical correlations. In our recent work [Phys. Rev. A 98, 012115 (2018)PRAHC32469-992610.1103/PhysRevA.98.012115], we considered a protocol - which we call the greedy local thermometry protocol - for estimating the temperature of thermal equilibrium states from local measurements, elucidating the role of diagonal discord in enhancing the protocol sensitivity in the high-temperature limit. In this paper, we extend our results to a general greedy local parameter estimation scenario. In particular, we introduce a quantum discord - which we call discord for local metrology - to quantify the nonclassical correlations induced by the local optimal measurement on the subsystem. We demonstrate explicitly that discord for local metrology plays a role in sensitivity enhancement in the high-temperature limit by showing its relation to loss in quantum Fisher information. In particular, it coincides with diagonal discord for estimating a linear coupling parameter.

Original languageEnglish (US)
Article number052318
JournalPhysical Review A
Issue number5
StatePublished - May 13 2019
Externally publishedYes

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics


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