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.
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.
This study aims to investigate the decoherence of the quantum correlation dynamics of two qubit nitrogen-vacancy (NV) centres through local quantum uncertainty (LQU), local quantum Fisher information (LQFI), and concurrence. Using an intrinsic decoherence model, our study investigates how increasing zero-field splitting, external magnetic fields, external electric control fields, dipole-dipole coupling and decoherence affect the generated correlations between two NV centers. It is shown that the system with two nitrogen-vacancy centres can generate strong correlations with certain parameters of zero-field splitting, external magnetic fields, external electric control fields and dipole-dipole coupling. With weak intrinsic decoherence, the generated LQFI, LQU and concurrence exhibit oscillating generations with the same frequency. Most of the time, LQFI and LQU exhibit the same Wigner-Yanase-Fisher correlation, except during strong entanglement intervals. Furthermore, the ability of interactions within a two-qubit system of NV centers to generate two-qubit correlations is weakened by increasing external magnetic fields and zero-field splitting fields. Conversely, increasing external electric control fields and dipole-dipole couplings strengthen the ability of the interactions to generate correlations. Finally, we investigated how an increase in intrinsic decoherence coupling significantly degrades the generated correlations. We also investigated how increasing the external magnetic field, the external electric control field and the dipole-dipole coupling significantly affects these correlation degradations.
Abstract We study the thermal evolution of entanglement, Bell non-locality, quantum steering, and correlated coherence in a system constituted of two nitrogen vacancy (NV) centers with dipole-dipole interaction and subjected to an external magnetic field. From the results, we observe that correlated coherence is more resilient than the other resources, so quantum tasks based on correlated coherence survive over a wider temperature range than those relying on non-local quantum correlations: correlated coherence remains nonzero up to k B T ≈ 41.7 GHz, whereas the other three measures vanish below k B T ≈ 0.6 GHz. We also reveal a distinct hierarchy of resilience of these quantum correlation metrics: Bell non-locality is the most fragile resource, followed by Einstein-Podolsky-Rosen (EPR)-steering and negativity. The results also indicate that the NV center parameters can be tuned for the enhancement and preservation of the quantum correlations within this system against thermal fluctuations.
Quantum correlations and coherence in a two-qubit anisotropic XY under magnetic field
We study thermal quantum correlations and coherence in Heisenberg XY model with anisotropic interactions under a uniform magnetic field $ B $. Using concurrence C, local quantum uncertainty (LQU), Bell-Clauser-Horne-Shimony-Holt (CHSH) nonlocality $ \mathbb{B}$, and coherence Cl as quantifiers, we analyze how magnetic anisotropy $ δ_m $, coupling anisotropy $ δ_c $, Dzyaloshinskii-Moriya (DM) interaction $ D $, temperature $ T $, and magnetic field $ B $ modulate quantum resources. At low temperatures and relevant magnetic fields, the entanglement is maximized, but exhibits sudden death for $ δ_m = 0 $, which turns into a smooth decay as $ δ_m $ increases, highlighting its stabilizing role. LQU shows that stronger anisotropy suppresses quantum correlations, while $ \mathbb{B} $ induces a non-monotonic response peaking at a critical field $ B_c .Bell−CHSHnonlocalityviolations( \mathbb{B} > 2 $) persist below $ B_c ,butthermalnoise( T \geq 1 $) suppresses them. Coherence $ C_l $ is most robust to thermal fluctuations, especially for high δm, which also dampens abrupt quantum phase transitions. The DM interaction is essential for entanglement generation, with $ D $ and anisotropy synergistically enhancing correlation resilience. We identify a hierarchy of thermal degradation: nonlocality ($ \mathbb{B} )vanishesfirst,followedbyentanglement( C $), then general quantum correlations (LQU), while coherence $ C_l $ persists the longest. These results demonstrate tunable control of quantum resources via anisotropy and external parameters, providing insights for the design of robust spin-based quantum technologies.
Abstract We employ entanglement negativity, local quantum uncertainty (LQU), and local quantum Fisher information (LQFI) to characterize thermal entanglement between two XYZ-Heisenberg-qubit states under the influence of Dzyaloshinsky-Moriya(DM) and Kaplan-Shekhtman-Entin-Wohlman-Aharony (KSEA) interactions, as well as a magnetic field and thermal equilibrium temperature. A comparative examination reveals similar behaviors among these correlation measures. For the antiferromagnetic scenario, we observe that increasing the DM interaction parameter D z enhances thermal entanglement. Conversely, in the ferromagnetic case, the behavior of thermal entanglement differs with varying D z . Additionally, employing Kraus operators, we explore the performance of these quantifiers under decoherence. Notably, LQFI exhibits greater robustness than negativity and LQU, even displaying a frozen phenomenon at some time under dephasing effects.
Quantum entanglement, as one of the most fundamental features of quantum theory, is the primary source of nonclassical correlations between subsystems and plays a crucial role in quantum energy and information transport phenomena. Investigating the thermal behavior of entanglement in simple systems, such as two-qubit models, provides an effective framework for analyzing the fundamental mechanisms governing quantum heat conduction. In this study, a two-qubit system with anisotropic interactions of the Dzyaloshinskii–Moriya (DM) and KSEA types was examined under an external magnetic field. To characterize the quantum correlations, two complementary measures are employed: negativity as an indicator of entanglement, and local quantum Fisher information (LQFI) as a measure of quantum correlations beyond entanglement. Numerical analysis reveals that the anisotropic structure of spin–spin interactions play a decisive role in the stability of entanglement at various temperatures. In particular, the presence of both DM and KSEA components can enhance the preservation of quantum correlations in the low-temperature regime, whereas the external magnetic field tends to suppress them. These findings provide new insights into the role of quantum correlations in the thermal processes of small-scale systems.
In this work, we demonstrate that the thermal nonclassical correlations can enhance and become more stable under the magnetic field and second-order spin–orbit interaction effect. Also, we show that the local quantum uncertainty measure can reveal purely quantum correlations beyond other quantifiers of correlations. Our analytical model describes a Heisenberg XYZ two-spin system with an inhomogeneous magnetic field and spin–orbit interaction. A special emphasis is devoted to local quantum uncertainty, concurrence, and Bell-nonlocality measures to investigate the correlations of the bipartite-system at the equilibrium temperature. Our results indicate that temperature, magnetic field, and magnetic field inhomogeneity with DMI and Kaplan–Shekhtman–Entin-Wohlman–Aharony (KSEA) exchanges all play a role in determining the degree of correlation between the quantum spins to some extent. The KSEA interaction greatly enhances the quantum correlation in the system whereas quantum quantifiers are more stable under the influence of the external magnetic field, especially when inhomogeneous and homogeneous magnetic field are near to zero. Furthermore, these findings suggest that the thermal LQU captures a stronger quantum correlation than the Bell-nonlocality and entanglement measures.