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arXiv:2609.13744 · Physical Review Letters

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

Shuo Ren, Rui-Jian Liang, Qi-Cheng Hu, Zhen-Xuan He, Ji-Yang Zhou, Wu-Xi Lin, Zhi-He Hao, Tao Tu, Jin-Shi Xu, Chuan-Feng Li, Guang-Can Guo

quant-phSubmitted Sep 12, 2026• Announced Sep 15, 2026• 0 citations
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Abstract

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.

Journal reference
Phys. Rev. Lett. 137, 100803 (2026)
DOI
10.1103/454t-n78h
Comments
Published in Physical Review Letters 137, 100803 (2026)

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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.
Solid-state color centers are promising candidates for nodes in quantum network architectures. However, realizing scalable and fully functional quantum nodes, comprising both processor and memory qubits with high-fidelity universal gate operations, remains a central challenge in this field. Here, we demonstrate a fully functional quantum node in silicon carbide, where electron spins act as quantum processors and nuclear spins serve as quantum memory. Specifically, we design a pulse sequence that combines dynamical decoupling with hyperfine interactions to realize decoherence-protected universal gate operations between the processor and memory qubits. Leveraging this gate, we deterministically prepare entangled states within the quantum node, achieving a fidelity of 90%, which exceeds the fault-tolerance threshold of certain quantum network architectures. These results open a pathway toward scalable and fully functional quantum nodes based on silicon carbide.
Quantum photonic integrated circuits are reshaping quantum networks and sensing by providing compact, efficient platforms for practical quantum applications. Despite continuous breakthroughs, integrating entangled registers into photonic devices on a CMOS-compatible platform presents significant challenges. Herein, we present single electron-nuclear spin entanglement and its integration into a silicon-carbide-on-insulator (SiCOI) waveguide. We demonstrate the successful generation of single divacancy electron spins and near-unity spin initialization of single 13C nuclear spins. Both single nuclear and electron spin can be coherently controlled and a maximally entangled state with a fidelity of 0.89 has been prepared under ambient conditions. Based on the nanoscale positioning techniques, the entangled quantum register has been further integrated into SiC photonic waveguides for the first time. We find that the intrinsic optical and spin characteristics of the register are well preserved and the fidelity of the entangled state remains as high as 0.88. Our findings highlight the promising prospects of the SiCOI platform as a compelling candidate for future scalable quantum photonic applications. Silicon-carbide-on-insulator is a promising platform for scalable quantum photonic circuits. Here the authors demonstrate the integration of a single electron-nuclear spin register into silicon-carbide-on-insulator waveguides, which is an important step toward CMOS-compatible quantum photonic devices.
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.
Multipartite entanglement is an essential aspect of quantum systems, needed to execute quantum algorithms, implement error correction and achieve quantum-enhanced sensing. In solid-state quantum registers such as nitrogen-vacancy centres in diamond, entangled states are typically created using sequential, pairwise gates between the central electron and individual nuclear qubits. This sequential approach is slow and suffers from crosstalk errors. Here we demonstrate a parallelized multi-qubit entangling gate to generate a four-qubit Greenberger-Horne-Zeilinger state using a room-temperature nitrogen-vacancy centre in only 14.8 μs-ten times faster than that using sequences of two-qubit gates and close to the fundamental limit set by the hyperfine coupling frequencies. Parallel three-qubit gates are also realized with all-nuclear-qubit subsets. The entangled states are verified by measuring multiple quantum coherences. The four-qubit parallel gate has a fidelity of 0.92(4), whereas the sequential four-qubit gate fidelity is only 0.69(3). The approach is generalizable to other solid-state platforms, and it lays the foundation for scalable generation and control of entanglement in practical devices.