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Laser Physics Letters

Visibility thresholds and quantum advantage time for coupled NV-center qutrits under dephasing

Fahad Aljuaydi, Heba Allhibi, Emad K. Jaradat, Muhammad Noman

Published Jul 1, 2026• 0 citations
Publisher

Abstract

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.

DOI
10.1088/1612-202x/ae8167

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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.
Abstract We explore the utility of quantum spin squeezing in quantum magnetometry, focusing on three-level (qutrit) Nitrogen-Vacancy (NV) centers within diamond, utilizing a standard Ramsey interferometry pulse protocol. Our investigation incorporates the effects of dephasing and relaxation on NV centers' dynamics during Ramsey measurements, modeled via the Lindblad quantum master equation. We conduct a comparative analysis between the metrological capabilities of a single NV center and a pair of NV centers, considering Quantum Fisher Information both with and without spin squeezing. The quantum correlations between NV centers are assessed through the evaluation of the Kitagawa-Ueda spin squeezing parameter within a two-level manifold. Additionally, parallel calculations are conducted using a two-level model (qubit) for NV centers. Our findings reveal that leveraging qutrits and spin squeezing yields enhanced magnetometric precision, albeit constrained by dephasing effects. Nevertheless, even in the absence of dynamical decoupling methods to mitigate environmental dissipation, strategic timing of squeezing and free evolution can sustain the advantages of qutrit-based magnetometry.
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.
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.
The nitrogen vacancy (NV) center in diamond, a well-studied, optically active spin defect, is the prototypical system in many state of the art quantum sensing and communication applications. In addition to the enticing properties intrinsic to the NV center, its diamond host's nuclear and electronic spin baths can be leveraged as resources for quantum information, rather than considered solely as sources of decoherence. However, current synthesis approaches result in stochastic defect spin positions, reducing the technology's potential for deterministic control and yield of NV-spin bath systems, as well as scalability and integration with other technologies. Here, we demonstrate the use of theoretical calculations of electronic central spin decoherence as an integral part of an NV-spin bath synthesis workflow, providing a path forward for the quantitative design of NV center-based quantum sensing systems. We use computationally generated coherence data to characterize the properties of single NV center qubits across relevant growth parameters to find general trends in coherence time distributions dependent on spin bath dimensionality and density. We then build a maximum likelihood estimator with our theoretical model, enabling the characterization of a test sample through NV T2* measurements. Finally, we explore the impact of dimensionality on the yield of strongly coupled electron spin systems. The methods presented herein are general and applicable to other qubit platforms that can be appropriately simulated.
Nitrogen-vacancy (NV) centers in diamond have emerged in the last decade as a prominent platform for quantum technologies. As for any qubit system, a good understanding of their local environment is crucial to build quantum devices protected from detrimental noise. Here, we describe in detail a method to spectroscopically characterize the spin bath around an NV center, even when the NV coherence time is short, and identify the coherent coupling with the nearest nuclear spins. In the regime of weak qubit-bath coupling, the acquired knowledge of the bath reliably predicts the qubit dynamics under different controls.
Abstract Nitrogen-vacancy (NV) centers in diamond have been developed into essential hardware units for a wide range of solid-state-based quantum technology applications. While such applications require the long spin coherence times of the NV centers, they are often limited due to decoherence. In this study, we theoretically investigate the decoherence of NV-spin ensembles induced by nitrogen impurities (P1 centers), which are one of the most dominant and inevitable magnetic field noise sources in diamond. We combined cluster correlation expansion and density functional theory to compute the Hahn-echo spin-coherence time of the NV centers for a broad range of P1 concentrations. Results indicate a clear linear dependence of T2 on P1 concentrations on a log scale with a slope of −1.06, which is in excellent agreement with previous experimental results. The interplay between the Jahn–Teller effect and the hyperfine interaction in the P1 center plays a critical role in determining the bath dynamics and the resulting NV decoherence. Our results provide a theoretical upper bound for the NV-spin T2 over a wide range of P1 densities, serving as a key reference for materials optimization and spin bath characterization to develop highly coherent NV-based devices for quantum information technology.