Develops modular self-duality for local states in QFT via symmetrized Araki relative entropy and defines the associated type-III BKM susceptibility, with exact quadratic realizations for free scalar fields on wedges and chiral U(1) currents on half-lines.
Quantum Fisher information and the curvature of entanglement
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abstract
We explore the relationship between quantum Fisher information (QFI) and the negative of the second derivative of concurrence with respect to the coupling between two qubits, referred to as the curvature of entanglement (CoE). The two-qubit system serves as a minimal model to study the connection between QFI and dynamically generated entanglement in scenarios where the measured quantity is a two- or many-body coupling strength. We analyze in detail the pure-state lossless case for which general results can be inferred and we also consider a simple interaction Hamiltonian in the case of one form of loss applied to the qubits. For a two-qubit quantum probe used to estimate the coupling constant appearing in the interaction Hamiltonian we show, for certain initial conditions, that there are times such that CoE = QFI. These times can be associated with the concurrence, viewed as a function of the coupling parameter, being a maximum. We examine the time evolution of the concurrence of the eigenstates of the symmetric logarithmic derivative (SLD). Measurements using the SLD eigenstates as basis are optimal for saturating the quantum Cramer bound. We show that, for several families of initially separable and initially entangled states, the SLD eigenstates are simple product states when CoE = QFI.
years
2026 4verdicts
UNVERDICTED 4representative citing papers
Exact expressions for thermal concurrence, its first and second derivatives, and bounds are derived establishing that thermal quantum Fisher information constrains the response and robustness of entanglement to temperature variations in interacting two-qubit thermal states.
For two interacting qubits the reduction in concurrence from fluctuations in interaction strength is bounded by the quantum Fisher information with respect to that strength.
Local quantum Fisher information and Bloch vector behavior characterize quantum crossovers where global indicators like steering ellipsoid volume remain insensitive.
citing papers explorer
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Modular Self-Duality, Symmetrized Relative Entropy, and Bogoliubov--Kubo--Mori Susceptibility in Quantum Field Theory
Develops modular self-duality for local states in QFT via symmetrized Araki relative entropy and defines the associated type-III BKM susceptibility, with exact quadratic realizations for free scalar fields on wedges and chiral U(1) currents on half-lines.
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Entanglement response to Temperature in Interacting Two-Qubit Thermal States
Exact expressions for thermal concurrence, its first and second derivatives, and bounds are derived establishing that thermal quantum Fisher information constrains the response and robustness of entanglement to temperature variations in interacting two-qubit thermal states.
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Information-Geometric Bound on the Robustness of Entanglement Generation
For two interacting qubits the reduction in concurrence from fluctuations in interaction strength is bounded by the quantum Fisher information with respect to that strength.
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Quantum Crossovers Revealed by Local Measurements
Local quantum Fisher information and Bloch vector behavior characterize quantum crossovers where global indicators like steering ellipsoid volume remain insensitive.