This extension method advances the characterization of NV centers in silicon carbide (SiC) by incorporating optimization strategies, machine learning (ML), error correction, and advanced sensing protocols. While the base method validated NV centers in 4H-SiC and 6H-SiC as promising solid-state qubits, our extension aims to enhance their performance and scalability for quantum technologies. First, we identified an optimal NV ensemble density of 1.0 × 10¹⁶ cm⁻3, balancing signal strength with minimized dipole–dipole interactions, thereby maximizing collective coherence. Second, a machine learning framework was developed to optimize experimental conditions, scanning laser power, excitation wavelength, and temperature to improve phase coherence time (T₂) by nearly two-fold. Third, advanced quantum sensing protocols were benchmarked, including Ramsey, Spin-Echo, CPMG, XY-8, and ML-optimized pulse sequences, achieving up to 3.5× higher sensitivity compared to conventional spin-echo. Fourth, dynamical decoupling (N=16) was applied to mitigate decoherence, extending T₂ up to ~60 μs at room temperature. Finally, error correction simulations at the NV ensemble level demonstrated logical error rate reductions by nearly two orders of magnitude, showcasing fault-tolerance potential. Overall, this extension transforms NV–SiC centers from characterized quantum defects into a practical platform with enhanced coherence, improved sensing capabilities, and integrated error correction. These results position SiC NV ensembles as a scalable candidate for next-generation quantum computing
This extension method advances the characterization of NV centers in silicon carbide (SiC) by incorporating optimization strategies, machine learning (ML), error correction, and advanced sensing protocols. While the base method validated NV centers in 4H-SiC and 6H-SiC as promising solid-state qubits, our extension aims to enhance their performance and scalability for quantum technologies. First, we identified an optimal NV ensemble density of 1.0 × 10¹⁶ cm⁻3, balancing signal strength with minimized dipole–dipole interactions, thereby maximizing collective coherence. Second, a machine learning framework was developed to optimize experimental conditions, scanning laser power, excitation wavelength, and temperature to improve phase coherence time (T₂) by nearly two-fold. Third, advanced quantum sensing protocols were benchmarked, including Ramsey, Spin-Echo, CPMG, XY-8, and ML-optimized pulse sequences, achieving up to 3.5× higher sensitivity compared to conventional spin-echo. Fourth, dynamical decoupling (N=16) was applied to mitigate decoherence, extending T₂ up to ~60 μs at room temperature. Finally, error correction simulations at the NV ensemble level demonstrated logical error rate reductions by nearly two orders of magnitude, showcasing fault-tolerance potential. Overall, this extension transforms NV–SiC centers from characterized quantum defects into a practical platform with enhanced coherence, improved sensing capabilities, and integrated error correction. These results position SiC NV ensembles as a scalable candidate for next-generation quantum computing
Solid-state color-center spin defects provide a versatile platform for quantum sensing with applications ranging from nanoscale magnetometry to thermometry and electrometry. This review surveys recent progress in nitrogen-vacancy centers in diamond and defect spins in silicon carbide (SiC), with emphasis on their material properties, fabrication strategies, and coherence engineering. Key defect creation and optimization techniques, including ion implantation, femtosecond laser writing, focused ion beam nanofabrication, isotopic engineering, and surface passivation, are discussed in the context of improving spin coherence and optical performance. Fundamental quantum measurement protocols, optically detected magnetic resonance, Rabi oscillations, Ramsey interferometry, and spin echo, are reviewed as a hierarchical framework for characterizing spin control, dephasing, and intrinsic coherence. The review further highlights microscale sensing architectures and examines the growing role of machine learning in pulse optimization, adaptive estimation, and data-driven imaging. Finally, current challenges and future directions are outlined, focusing on scalability, environmental robustness, and autonomous operation. Together, these developments position diamond and SiC color centers as leading platforms for next-generation solid-state quantum sensors.
The unique spin-optical properties of NV defects in SiC, coupled with silicon carbide's advanced technology compared to diamond, make them a promising candidate for quantum technology applications. In this study, using photoinduced pulse ESR at 94 GHz (3.4 T), we reveal the room temperature spin coherence of NV defects in 6H-28SiC, purified to reduce 29Si concentration to ≈1%, four times below its natural level. We demonstrate room temperature (300 K) Hahn-echo coherence time T2 = 23.6 μs, spin–lattice relaxation time T1 = 0.1 ms, and coherent control over optically polarized NV spin states through Rabi nutation experiments. We reveal long inhomogeneous dephasing time T2* = 1.5 μs, which is about five times greater than that measured for NV defects in SiC with natural isotopic content. Our observations highlight again the potential of NV defects in 6H-28SiC, which exhibit near-infrared optical excitation and emission properties compatible with O-band fiber optics, as promising candidates for applications in quantum sensing, communication, and computation.
Silicon carbide (SiC) has become a key player in the realization of scalable quantum technologies due to its ability to host optically addressable spin qubits and wafer-size samples. Here, we have demonstrated optically detected magnetic resonance (ODMR) with resonant excitation and clearly identified the ground state energy levels of the NV centers in 4H-SiC. Coherent manipulation of NV centers in SiC has been achieved with Rabi and Ramsey oscillations. Finally, we show the successful generation and characterization of single nitrogen vacancy (NV) center in SiC employing ion implantation. Our results highligh the key role of NV centers in SiC as a potential candidate for quantum information processing.
Nitrogen-vacancy (NV) centers in single-crystal CVD diamond are promising candidates for quantum sensing due to their remarkable optical and spin properties [1]. These defects exhibit stable photoluminescence (PL), long spin coherence times, and high sensitivity to external fields [2]. In this study, we present a room-temperature PL characterization of NV centers excited with a 532 nm laser. The setup was optimized for high signal-to-noise ratio and spectral resolution. Key parameters analyzed include emission intensity, zero-phonon line (ZPL) at ~637 nm, phonon sidebands, and the charge state distribution between NV⁰ and NV⁻. The NV⁻ state, crucial for spin-based sensing, is evaluated to understand its stability under different nitrogen doping conditions [3]. The relative intensities of NV⁰ and NV⁻ provide insights into nitrogen incorporation and vacancy formation. These results contribute to optimizing synthesis conditions for enhanced NV⁻ concentration, supporting the advancement of diamond-based quantum sensing technologies.
Because of their high sensitivity, quantum materials are extremely promising for new technologies. The main challenge lies in maintaining a sufficiently quantum coherence times for quantum computation or quantum sensing systems. NV centers in diamond which are point defects consisting of a substitutional nitrogen atom neighboring an atomic vacancy, where an electron pair can reside in a triplet state – are ideal candidates for the development of industrial-scale quantum systems. These spin states exhibit ms-long coherence times at room temperature and can be manipulated optically, hence opening interesting perspectives for sending magnetic fields with high sensitivity1.At HiQuTe Diamond, we take up the challenge of mastering the entire nitrogen-doped diamond production chain synthesized by Microwave Plasma-Assisted Chemical Vapor Deposition (MPACVD). We aim at creating affordable diamonds specially engineered to achieve long coherence times with high NV density and high doping uniformity. This quest require to overcome the impact of several external factors that contribute to electron spin decoherence. First, the chemical composition of the diamond, specifically the types and concentrations of impurities within the diamond matrix (such as substitutional nitrogen NS, NV centres, mono-vacancies and clusters, hydrogen, etc.), as well as their electrical charge states (NS⁰, NS⁺, NV⁰, NV⁻) should be carefully controlled. Thanks to extensive scientific research conducted over the past decade, combined with our own R&D efforts, we are now able to quantify these parameters using experimental techniques compatible with industrial applications (Raman and UV-Vis spectroscopy) and compare our results with key performance indicators2. Second, we study the relationship between coherence (T2*) and strain inhomogeneities in our diamond layers, which we analyse using birefringence measurements. Our findings demonstrate our capability to produce CVD diamond layers with reduced strain and extended defect and confirm that strain could be a critical limiting factor for T2*.In this poster, I will review the efforts carried out at HiQuTe Diamond to develop specific material that is well suited for quantum sensing applications.References1.Barry, J. F., Schloss, J. M., Bauch, E., Turner, M. J., Hart, C. A., Pham, L. M., & Walsworth, R. L. (2020). Sensitivity optimization for NV-diamond magnetometry. Reviews of Modern Physics, 92(1), 015004.2.Langer, J. (2022). Quantum-grade diamond for cavity-based solutions. Fraunhofer Verlag.
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.