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Superconductors, Magnetism, Quantum Metrology, and Computing
Published in Miguel A. Esteso, Ana Cristina Faria Ribeiro, A. K. Haghi, Chemistry and Chemical Engineering for Sustainable Development, 2020
Francisco Torrens, Gloria Castellano
Quantum entanglement lies at quantum-information and -metrology heart, in which, with a colossal amount of quantum Fisher information (QFI), entangled systems were ameliorated to result a better resource scheme. Notwithstanding, noisy channels eject QFI substantially. Falaye group investigated how N-quantum binary digit (bit) (qubit) Greenberger–Horne–Zeilinger’s (GHZ) state QFI is ejected, when subjected to decoherence channels: bitphase flip and generalized amplitude damping, which were experimentally induced.35 They determined the evolution under the channels, deduced the eigenvalues and derived QFI. They found that when no interaction with the environment exists, Heisenberg’s limit was achieved via rotations along z-direction. They showed that N-qubit-GHZ-state maximal mean QFI (Fmax) dwindled as decoherence (d) rose, because of information low from the system to the environment, until d = 0.5, then revived to form a symmetry around d = 0.5, which revival was as a consequence of environment memory eject, which led to information back-ow from the environment to the system. The d > 0.5 leads to a situation where more noise yields more efficiency. They showed that at finite temperature, QFIs decayed more rapidly than at infinite one. They revealed that QFI could be enhanced by adjusting environmental temperature.
Dynamics of local quantum uncertainty and local quantum fisher information for a two-qubit system driven by classical phase noisy laser
Published in Journal of Modern Optics, 2021
In order to describe the quantum correlation dynamics, we here employ the local quantum uncertainty (LQU) and local quantum Fisher information (LQFI) as a measure of quantum correlations. According to reference [4] proposed by Girolami et al, the LQU is defined as the minimal quantum uncertainty in a quantum state due to a measurement of any local observable operator, namely, where is the skew information referring to non-commutation between a bipartite quantum state and a Hermitian observable operator acting on the subsystem A, and is the identity operator acting on the subsystem B. The min sign requirers a minimization procedure over the set of observable. For any bipartite systems, an explicit closed form of LQU has been derived [4] where are the eigenvalues of the matrix whose matrix elements are defined by here represent the Pauli matrices with .