ABSTRACT We study quantum resources in tilted‐Dirac materials using a thermal state and reservoir‐driven dynamics in dissipative weak‐coupling and memory‐bearing strong‐coupling regimes. In contrast to the usual treatments based on the Bellomo formalism and relying on Bell or Werner states, the present approach starts from a physically motivated thermal state of two qubits whose initial properties are determined by the system temperature and the velocity parameters of the underlying Dirac material. The subsequent dynamics is modeled using the Bellomo formalism for two independent qubits, each locally coupled to an independent reservoir. To characterize the evolution, we analyze coherence quantified by the ‐norm and local quantum Fisher information. Weak, effectively Markovian coupling yields monotonic coherence decay, while local quantum Fisher information depends more strongly on parameters, especially at low reservoir temperatures; varying velocity parameters together obscures their individual effects. With strong, memory‐bearing coupling, coherence remains suppressed at long times, whereas local quantum Fisher information decreases then recovers to a large asymptotic value. The two measures thus respond differently to thermal, material, and reservoir effects, without implying general practical metrological superiority of local quantum Fisher information.
Abstract This study explores the temporal evolution of local quantum Fisher information and coherence in a graphene monolayer subjected to a polarized electromagnetic field, revealing significant effects driven by system parameters. In the absence of the field, the analysis highlights the crucial role of the initial state's purity in the dynamics of both local quantum Fisher information and coherence, influencing their amplitude and decay over time. Introducing an electromagnetic field unveils a strong dependence of these quantities on the polarization and amplitude parameters. For linear polarization, local quantum Fisher information and coherence reach their maximum values at specific field phases, while for circular polarization, the system's response becomes more complex, exhibiting pronounced variations and a gradual decrease in coherence at higher field intensities. These findings emphasize the importance of controlling electromagnetic parameters to manipulate quantum information in graphene and open up new prospects for applications in quantum electronics and information processing.
Abstract The thermal behavior of quantum correlations is explored in a two‐qubit system based on nitrogen‐vacancy (NV) centers, using Local Quantum Fisher Information (LQFI), Local Quantum Uncertainty (LQU), and concurrence as quantifiers. These results show that entanglement, measured byconcurrence (CE), decays rapidly with increasing temperature, whereas coherence‐based measures such as LQFI and LQU display greater resilience. The strength of zero‐field splitting plays a key role in shaping quantum correlations, significantly suppressing entanglement at higher values while helping to preserve coherence. External magnetic and electric fields further influence these dynamics–magnetic fields tend to suppress entanglement, while electric fields accelerate its degradation. Dipole–dipole interactions enhance the initial quantum correlations but have a limited effect on their thermal decay. Overall, these findings underscore the robustness of coherence‐based quantum resources and suggest that, while dipole–dipole coupling is more effective at regulating quantum correlations, optimal tuning of system parameters can significantly improve both the generation and preservation of these correlations at finite temperatures.
In this work, we investigate the relationship between quantum coherence and multiparameter quantum estimation in a graphene-based system. We focus on the estimation of two relevant physical parameters, namely the temperature
T and the wave vector
kx, and analyze how their variations affect both quantum coherence and the achievable metrological precision. The minimum variances associated with the estimation process are evaluated through the quantum Cramér--Rao bound within both simultaneous and independent estimation schemes. Our results show that quantum coherence is enhanced in the low-temperature regime and around
kx=0, while it decreases progressively as either the temperature or the wave vector increases. However, the regions where coherence is maximal do not necessarily coincide with those of optimal estimation precision. In particular, the variance associated with temperature estimation exhibits a divergent behavior near
T=0, indicating that the system becomes weakly sensitive to small temperature variations in this regime. By contrast, the estimation of the wave vector
kx is more directly related to the coherence properties of the system, with improved precision obtained near
kx=0. Furthermore, we introduce the ratio
Γ to compare the total variances obtained from the independent and simultaneous estimation schemes. This quantity provides a useful measure of the relative difference between the two strategies when the parameters are estimated separately or jointly.
Abstract We investigate nonclassical correlations via negativity, local quantum uncertainty (LQU) and local quantum Fisher information (LQFI) for two-dimensional graphene lattices. The explicitly analytical expressions for negativity, LQU and LQFI are given. The close forms of LQU and LQFI confirm the inequality between the quantum Fisher information and skew information, where the LQFI is always greater than or equal to the LQU, and both show very similar behavior with different amplitudes. Moreover, the effects of the different system parameters on the quantified quantum correlation are analyzed. The LQFI reveals more nonclassical correlations than LQU in a two-dimensional graphene lattice system.
Abstract This study explores the dynamics of a two-qubit superconducting charge system, a prevalent technology in quantum computing. We utilize logarithmic negativity and local quantum Fisher information to gauge the entanglement and correlations within this system. Our findings indicate a significant influence of temperature on the system, leading to a reduction in both measures. However, adjusting system parameters can enhance these quantum quantifiers. Furthermore, we note that the local quantum Fisher information exhibits greater resilience to temperature-induced degradation compared to logarithmic negativity.