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arXiv:2512.20281

Localization and coherent control of 25 nuclear spins in Silicon Carbide

Pierre Kuna, Erik Hesselmeier-Hüttmann, Phillip Schillinger, Felix Gloistein, István Takács, Viktor Ivády, Wolfgang Knolle, Jawad Ul-Hassan, Jörg Wrachtrup, Vadim Vorobyov

quant-phphysics.opticsSubmitted Dec 23, 2025• Announced Dec 24, 2025
arXivHTMLPDF

Abstract

Optically addressable spin defects are excellent candidate platform for quantum sensing and quantum network. Nuclear spins coupled to color centers naturally enable long lived quantum memories and local qubits registers. To fully leverage this potential precise characterization of the surrounding nuclear-spin environment augmented with refined DFT models is required. In this work, we report angstrom-level 3D localization of 25 nuclear spins around a single V2 center in 4H Silicon Carbide. Utilizing specially placed robust nuclear memory as a highly efficient readout ancilla for readout, we apply correlation based spectroscopy and by selecting multi-spin chains up to length four, we access and characterize extended nuclear spin cluster. Using the coupling map we reconstruct their couplings to the central electron spin and neighboring nuclei. This work paves the way towards advanced quantum register applications on Silicon Carbide platform.

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Room-Temperature Storage of Entanglement in a Silicon Carbide Quantum Node

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Robust entanglement at room temperature is a central challenge for solid-state quantum information processing and quantum-enhanced sensing. Here we demonstrate room-temperature storage of entanglement in a silicon carbide (SiC) quantum node by coherently transferring an electron-nuclear entangled state onto long-lived nuclear-spin memory qubits. Using a shallow single color center in 4H-SiC, conventionally denoted PL6, we realize a fully addressable three-qubit register composed of one electron-spin processor and two strongly coupled $^{29}$Si nuclear-spin memory qubits. This platform enables the deterministic generation of high-fidelity entangled states, including a nuclear-spin Bell state with a fidelity of $94 \pm 2\%$ and a three-qubit Greenberger-Horne-Zeilinger (GHZ)-type state with a fidelity of $89 \pm 4\%$. By implementing a SWAP-gate protocol in the strong hyperfine-coupling regime, the electron-nuclear entanglement is transferred to the nuclear-spin memory with a fidelity of $92.5 \pm 2.5\%$, extending the entanglement lifetime by a factor of 240. We further confirm the generality of this approach in an additional heterogeneous $^{29}$Si-$^{13}$C nuclear-spin register and, through a statistical survey of 200 single PL6 centers, show that multi-nuclear-spin registers occur naturally with probabilities above 10%. These results position shallow SiC color centers as a powerful platform for entanglement-assisted quantum sensing and scalable room-temperature quantum technologies.

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The ultimate motivation of my project is to address the possibility of building a quantum analogue of Internet of Things in order to improve the standards of quantum information processing. A distributed quantum computing network which is capable of achieving this goal, would require large sets of memory nodes capable of performing arbitrary quantum information protocols with high fidelity [1], [2]. So far, the challenge in this field has been in realizing such quantum memory nodes with features for scalable quantum computing. Solid state spins in 4H-Silicon Carbide (4H-SiC) owing to its material properties provides a suitable platform in achieving this goal wherein a controlled generation of highly coherent qubit registers using nuclear spins$(^{13}\mathrm{C} \ \text{or} \ {}^{\text{29}} \text{Si})$and silicon vacancy color centers$(V_{Si}^{-} \ \text{center})$| are possible[3], [4]. The magnetic dipole-dipole coupling between the isotope nuclear spins and the silicon vacancy color center can be tapped using microwave pulse (MW) sequence (as shown in Fig. 1(a)) for controlled driving of nuclear spin.

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Nano-integrated color centers in SiC with robust spin-photon interfaces and access to nuclear spin qubits

Florian Kaiser

We highlight our work [1] on nanophotonic integration of color centers in semiconductor silicon carbide (SiC). We show ion-assisted implantation and waveguide-integration of silicon vacancy centers (VSi) in 4H-SiC with nearly lifetime limited optical lines and record spin coherence times. We further show controlled coupling to nearby nuclear spin qubits. Our experiments can be performed at high temperatures (T=20 K), thus enabling fast and direct nuclear spin control. Our work shows that VSi centers in SiC are attractive for developing next-generation quantum (computational) networks based on optically interconnected spin-based qubit clusters. [1] Babin et al, Nature Materials, to appear (2021)

Quantum Computing, Communication, and Simulation•Mar 9, 2022•0 citations
Optically addressable spin defects are excellent candidate platform for quantum sensing and quantum network. Nuclear spins coupled to color centers naturally enable long lived quantum memories and local qubits registers. To fully leverage this potential precise characterization of the surrounding nuclear-spin environment augmented with refined DFT models is required. In this work, we report angstrom-level 3D localization of 25 nuclear spins around a single V2 center in 4H Silicon Carbide. Utilizing specially placed robust nuclear memory as a highly efficient readout ancilla for readout, we apply correlation based spectroscopy and by selecting multi-spin chains up to length four, we access and characterize extended nuclear spin cluster. Using the coupling map we reconstruct their couplings to the central electron spin and neighboring nuclei. This work paves the way towards advanced quantum register applications on Silicon Carbide platform.
Robust entanglement at room temperature is a central challenge for solid-state quantum information processing and quantum-enhanced sensing. Here we demonstrate room-temperature storage of entanglement in a silicon carbide (SiC) quantum node by coherently transferring an electron-nuclear entangled state onto long-lived nuclear-spin memory qubits. Using a shallow single color center in 4H-SiC, conventionally denoted PL6, we realize a fully addressable three-qubit register composed of one electron-spin processor and two strongly coupled 29^{29}29Si nuclear-spin memory qubits. This platform enables the deterministic generation of high-fidelity entangled states, including a nuclear-spin Bell state with a fidelity of 94±2%94 \pm 2\%94±2% and a three-qubit Greenberger-Horne-Zeilinger (GHZ)-type state with a fidelity of 89±4%89 \pm 4\%89±4%. By implementing a SWAP-gate protocol in the strong hyperfine-coupling regime, the electron-nuclear entanglement is transferred to the nuclear-spin memory with a fidelity of 92.5±2.5%92.5 \pm 2.5\%92.5±2.5%, extending the entanglement lifetime by a factor of 240. We further confirm the generality of this approach in an additional heterogeneous 29^{29}29Si-13^{13}13C nuclear-spin register and, through a statistical survey of 200 single PL6 centers, show that multi-nuclear-spin registers occur naturally with probabilities above 10%. These results position shallow SiC color centers as a powerful platform for entanglement-assisted quantum sensing and scalable room-temperature quantum technologies.
A distributed quantum network would require quantum nodes capable of performing arbitrary quantum information protocols with high fidelity. So far the challenge has been in realizing such quantum nodes with features for scalable quantum computing. We show here that using the solid-state spins in 4H-Silicon Carbide (4H-SiC) such a goal could be realized, wherein a controlled generation of highly coherent qubit registers using nuclear spins is possible. Using a controlled isotope concentration and coherent control we perform here atomistic modeling of the central spin system formed by the electron spin of a silicon vacancy color center (VSi−V_{Si}^-VSi−​-center) and the non-interacting nuclear spins. From this we lay out conditions for realizing a scalable nuclear-spin (13C^{13}C13C or 29Si^{29}Si29Si) register, wherein independent control of the qubits alongside their mutual controlled operations using the central electron spin associated to the VSi−V_{Si}^-VSi−​-center in 4H-SiC are achieved. Further, the decoherence and entanglement analysis provided here could be used to evaluate the quantum volume of these nodes. Our results mark a clear route towards realizing scalable quantum memory nodes for applications in distributed quantum computing networks and further for quantum information protocols.
The ultimate motivation of my project is to address the possibility of building a quantum analogue of Internet of Things in order to improve the standards of quantum information processing. A distributed quantum computing network which is capable of achieving this goal, would require large sets of memory nodes capable of performing arbitrary quantum information protocols with high fidelity [1], [2]. So far, the challenge in this field has been in realizing such quantum memory nodes with features for scalable quantum computing. Solid state spins in 4H-Silicon Carbide (4H-SiC) owing to its material properties provides a suitable platform in achieving this goal wherein a controlled generation of highly coherent qubit registers using nuclear spins(13C or 29Si)(^{13}\mathrm{C} \ \text{or} \ {}^{\text{29}} \text{Si})(13C or 29Si)and silicon vacancy color centers(VSi− center)(V_{Si}^{-} \ \text{center})(VSi−​ center)| are possible[3], [4]. The magnetic dipole-dipole coupling between the isotope nuclear spins and the silicon vacancy color center can be tapped using microwave pulse (MW) sequence (as shown in Fig. 1(a)) for controlled driving of nuclear spin.
Color centers that enable nuclear-spin control without RF fields offer a powerful route towards simplified and scalable quantum devices. Such capabilities are especially valuable for quantum sensing and computing platforms that already find applications in biology, materials science, and geophysics. A key challenge is the coherent manipulation of nearby nuclear spins, which serve as quantum memories and auxiliary qubits but conventionally require additional high-power RF fields which increase the experimental complexity and overall power consumption. Finding systems where both electron and nuclear spins can be controlled using a single MW source is therefore highly desirable. Here, using a modified divacancy center in silicon carbide, we show that coherent control of a coupled nuclear spin is possible without any RF fields. Instead, MW pulses driving the electron spin also manipulate the nuclear spin through hyperfineenhanced effects, activated by a precisely tilted external magnetic field. We demonstrate high-fidelity nuclear-spin control, achieving 89% two-qubit tomography fidelity and nearly T1-limited nuclear coherence times. This approach offers a simplified and scalable route for future quantum applications.
Quantum state readout is a key requirement for a successful qubit platform. In this work, we demonstrate a high-fidelity quantum state readout of a V2 center nuclear spin based on a repetitive readout technique. We demonstrate up to 99.5% readout fidelity and 99% for state preparation. Using this efficient readout, we initialize the nuclear spin by measurement and demonstrate its Rabi and Ramsey nutation. Finally, we use the nuclear spin as a long-lived memory for quantum sensing application of a weakly coupled diatomic nuclear-spin bath.
We highlight our work [1] on nanophotonic integration of color centers in semiconductor silicon carbide (SiC). We show ion-assisted implantation and waveguide-integration of silicon vacancy centers (VSi) in 4H-SiC with nearly lifetime limited optical lines and record spin coherence times. We further show controlled coupling to nearby nuclear spin qubits. Our experiments can be performed at high temperatures (T=20 K), thus enabling fast and direct nuclear spin control. Our work shows that VSi centers in SiC are attractive for developing next-generation quantum (computational) networks based on optically interconnected spin-based qubit clusters. [1] Babin et al, Nature Materials, to appear (2021)