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.
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.
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 Nitrogen-vacancy (NV) centers in diamond are a leading solid-state platform for quantum technologies. While often operated as qubits, their native ground state is a spin-1 triplet, making them natural qutrits. Here, we develop a quantitative framework to assess the performance of two coupled NV qutrits as a quantum resource in the presence of environmental noise. We model the system with a Hamiltonian including zero-field splitting, Zeeman, and dipole-dipole terms, and study its evolution under a phase-covariant dephasing channel characteristic of solid-state environments. For an Ohmic bath at zero temperature, we derive an exact analytical form for the decay of two-qutrit coherences. Applying this model to maximally entangled and isotropic states, we obtain closed-form expressions for teleportation fidelity and the visibility thresholds required to demonstrate Bell nonlocality and quantum steering. Our central result is a set of analytic formulas for the quantum advantage time, the duration for which these quantum tasks outperform their classical limits, as a function of the bath’s cutoff frequency. This framework provides direct, parameter-level guidance for designing and benchmarking experiments with coupled NV-center qutrits.
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.
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.
Hybrid quantum systems integrating superconducting qubits and nitrogen-vacancy (NV) center qutrits are promising for quantum information processing but are vulnerable to environmental dephasing. This study investigates the distinct dynamical behaviors of three facets of quantumness — total nonclassical correlations (Local Quantum Uncertainty (LQU)), quantum superposition ([Formula: see text] norm of coherence), and entanglement (Negativity) — in such a qubit–qutrit hybrid system subjected to non-Markovian dephasing noise. We reveal a clear hierarchy of robustness: coherence exhibits remarkably persistent oscillations, LQU decays with damped oscillations to a stable non-zero baseline, while entanglement proves most fragile, suffering periodic sudden death. Our central finding is the uniquely constructive role of the direct qubit–qutrit coupling strength, which robustly enhances all three quantum resources. In contrast, most other system parameters either accelerate decoherence or have complex, non-monotonic effects. These results clarify the different resilience levels of quantum resources and identify key parameters for preserving quantumness in noisy hybrid systems.
We investigate quantum correlations in a hybrid qubit-qutrit system subject to both axial and planar single-ion anisotropies, dipolar spin-spin interactions, and Dzyaloshinskii-Moriya (DM) coupling. Using Negativity, Measurement-Induced Non-locality (MIN), Uncertainty-Induced Nonlocality (UIN), and Bell nonlocality (as quantified by the CHSH inequality) as measures, we analyze the interplay between anisotropy parameters, magnetic fields, and temperature on the survival of quantum correlations. Our results demonstrate that Bell nonlocality and entanglement (Negativity) are highly sensitive to temperature and anisotropy, exhibiting sudden death under thermal noise, whereas MIN and UIN are significantly more robust. In particular, these discord-like and information-theoretic measures provide the largest baseline and persist even in parameter regions where entanglement vanishes, highlighting their suitability as a quantumness witness in realistic conditions. Notably, our Bell nonlocality study is tailored to the asymmetric qubit-qutrit setting by exploiting a recently developed qubit-qudit CHSH maximization framework. However, Bell nonlocality is confirmed to be the most fragile, surviving only in narrow parameter windows at low temperature. A key finding of this work is that we observe the fragility hierarchy: Bell nonlocality ⊆ Negativity ⊆ UIN(MIN) in the qubit-qutrit setting. These results provide deeper insight into the relative robustness of distinct quantum resources in anisotropic qubit-qutrit models, suggesting that quantum discord-like measures, such as MIN and UIN, may serve as more practical resources than entanglement for quantum information tasks in thermally active spin systems.