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Quantum Information Processing

Quantum Fisher information, quantum entanglement and correlation close to quantum critical phenomena

Cheng-cheng Liu, Dong Wang, Wen‐Yang Sun, Liu Ye

Published Jul 26, 2017• 30 citations
Publisher
DOI
10.1007/s11128-017-1674-z

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A clear relationship between the quantum version of Fisher information and the bipartite system entanglement has been explored recently. Known existing results for some quantum systems having strongly nonlocal correlations are still limited. In this paper, based on the interaction between a two-qubit and squeezed field, we investigate the correlation between the dynamical behavior of qubit-qubit entanglement and the quantum Fisher information (QFI). We focus on the effect of a number of photon multiplicity, low and high squeezing regime of the field on the dynamics of the QFI and entanglement quantifier. We show how the QFI and entanglement quantifier can be affected by the number of photon multiplicity and squeeze parameter during the time evolution of cases of absence and presence of dissipation effect. Our results exhibit the correlation between the entanglement quantifiers and the QFI with respect to the appearance of collapse and revival phenomena of the atomic inversion.
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Recently, researchers have found that not only entanglement but also quantum discord and even classical correlation can enhance the precision of parameter estimation. Thus the correlation which contributes quantum metrology should be treated as a new type of resource. In this paper, we directly construct a measure of the resource named as the relative quantum Fisher information (rQFI). It quantifies the improvement of QFI caused by correlations naturally. Operationally, rQFI quantifies the improvement of optimal precision achieved by joint measurement on a composite system, instead of the local measurement on the subsystem. Furthermore, rQFI itself is an alternative type of total correlation which captures effects of quantum entanglement, quantum discord, and classical correlation. It reduces to an entanglement measure for pure states. A detailed study for general two-qubit states is presented. Additionally, an alternative generalized discord measure can be extracted out of the rQFI.