Spin defects in silicon carbide (SiC) are promising candidates for integrated quantum photonics, offering long-lived spin states and near-infrared emission suitable for low-loss photonic integration and fibre-based quantum communication. However, light extraction from these defects remains challenging due the relatively high refractive index of SiC. Metalenses offer a compact approach to enhance light collection by engineering the wavefront directly at the material interface. Here, we design and fabricate monolithic metalenses from SiC bulk material that simultaneously operate at 860 and 1240 nm, matching with emission from the nitrogen vacancy and silicon vacancy colour centers. By independently engineering the phase response at both wavelengths, the metalens enables collection and polarization manipulation of the emitted light. We further employ the metalenses to demonstrate optically detected magnetic resonance of both defects simultaneously. These multifunctional metalenses provide a compact optical interface for scalable integrated SiC photonic devices.
Spin defects in silicon carbide (SiC) are promising candidates for integrated quantum photonics, offering long-lived spin states and near-infrared emission suitable for low-loss photonic integration and fibre-based quantum communication. However, light extraction from these defects remains challenging due the relatively high refractive index of SiC. Metalenses offer a compact approach to enhance light collection by engineering the wavefront directly at the material interface. Here, we design and fabricate monolithic metalenses from SiC bulk material that simultaneously operate at 860 and 1240 nm, matching with emission from the nitrogen vacancy and silicon vacancy colour centers. By independently engineering the phase response at both wavelengths, the metalens enables collection and polarization manipulation of the emitted light. We further employ the metalenses to demonstrate optically detected magnetic resonance of both defects simultaneously. These multifunctional metalenses provide a compact optical interface for scalable integrated SiC photonic devices.
Silicon carbide (SiC) is a promising platform for scalable quantum technologies owing to its well-established, wafer-scale industrial processing. SiC also hosts a variety of optically active color centres including the nitrogen vacancy defect that has a spin-triplet ground state. However, strong phonon coupling in the infrared range limits photon extraction from these defects. Here, we use nanophotonic structures, specifically micro-pillar and micro-disk resonators, to enhance optical collection and spin-readout. The micro-pillar geometry yields a 4-fold increase in photon collection, accompanied by a 2.4-fold reduction in spectral noise in optically detected magnetic resonance measurements. Consequently, the magnetic field sensitivity is improved by 24%. The large mode volume of the micro-disk supports resonances spanning 1150-1250 nm, enabling broadband coupling to nitrogen vacancy emission lines. Our results demonstrate that fabrication of scalable photonic structures efficiently improves performance of silicon carbide color centers for integrated quantum light generation and sensing.
Optically addressable solid-state spin defects are promising candidates for storing and manipulating quantum information using their long coherence ground-state manifold; individual defects can be entangled using photon-photon interactions, offering a path toward large-scale quantum photonic networks.Quantum computing protocols place strict limits on the acceptable photon losses in the system.These lowloss requirements cannot be achieved without photonic engineering, but are attainable if combined with state-of-the-art nanophotonic technologies.However, most materials that host spin defects are challenging to process: as a result, the performance of quantum photonic devices is orders of magnitude behind that of their classical counterparts.Silicon carbide (SiC) is well suited to bridge the classical-quantum photonics gap, since it hosts promising optically addressable spin defects and can be processed into SiC-on-insulator for scalable, integrated photonics.In this paper, we discuss recent progress toward the development of scalable quantum photonic technologies based on solid-state spins in silicon carbide, and discuss current challenges and future directions.
Quantum networks based on solid-state spin defects present a transformative approach to secure communication and distributed quantum computing, utilizing quantum entanglement and coherent spin–photon interfaces. Silicon carbide (SiC) stands out as a compelling material platform due to its unique combination of a wide bandgap, high optical nonlinearity, CMOS-compatible fabrication, and controllable spin-active defects. These intrinsic properties facilitate efficient photon emission, robust spin coherence at both room and cryogenic temperatures, and integration with photonic nanostructures. Recent advancements in defect engineering and micro-nanophotonics have unlocked the potential of SiC quantum nodes, which feature electron-nuclear spin systems for high-fidelity quantum operations and long-lived quantum memories. Key steps such as single-shot readout and spin-photon entanglement have been successfully demonstrated, bringing SiC closer to a real quantum network platform. This review offers a comprehensive overview of the advancements in SiC-based quantum networks, encompassing key aspects such as defect fabrication methodologies, optimization of spin-photon interfaces, and strategies for photonic integration. Additionally, it examines the existing challenges and outlines promising future directions in this rapidly evolving field.
Abstract Silicon carbide (SiC) is an excellent industrially compatible material, which has been widely used in high power electronic devices. Recently, spin defects in SiC have been found to be a high-quality spin-to-photon interface with long spin coherence time and high spin-selective optical transition. Spin states can be initialized and readout with extremely high fidelity. The infrared and even telecom fluorescence is suited for fiber communication with less scatting loss. The bandwidth of intrinsic zero-phonon-line emission can be manipulated by classical electrical devices. The achieved near lifetime-limited optical linewidths greatly increase the indistinguishability of photon emission and facilitate the connection with other narrowband absorption quantum systems, such as cold atoms, trapped ions, and rare-earth dopants in crystals. Moreover, spin defects coupled with photonic nanocavities have been demonstrated, which can greatly enhance the photon emission in the zero-phonon-line. The realization of controllable electron-nuclear spin entanglement further extends the memory-based quantum applications. In this perspective, we will briefly discuss the most recent development of spin defects in SiC. These results show that spin defects in SiC are desirable quantum platforms for quantum networking applications. We also discuss some of the current challenges and possible future development.
Defect based qubit systems like the nitrogen vacancy center in diamond have recently emerged as promising candidates for quantum technologies due to their combination of long coherence times, room temperature operation, and robust optical interface. In order to realize many of their proposed applications, defect qubits must be incorporated into scalable devices architectures consisting of photonic, mechanical, or electrical degrees of freedom. Despite much recent progress, many challenges remain for diamond growth and device fabrication. As an alternate approach, we engaged in a search for nitrogen vacancy center analogues in alternative materials with the hope of obtaining a greater degree of control over defect and material properties. Ultimately, we discovered that divacancy-related point defects in all three of the most common forms of silicon carbide- termed 4H, 6H, and 3C- act as analogues to the nitrogen vacancy center in diamond. We chose to focus our research primarily on defects in 3C silicon carbide (termed 'Ky5' defects) because of its availability as a single crystal heteroepitaxial thin film grown on silicon, an advantage that greatly facilitates the fabrication of functional devices. We characterized the spin and optical properties of Ky5 defects in thin film geometries and observed many similarities to the nitrogen vacancy center. We performed the first measurements of spin dynamics in 3C silicon carbide and demonstrate coherent control of defect spins up to room temperature and observe coherence times of up to 22 microseconds. To demonstrate their use in real devices, we designed, fabricated, and characterized photonic crystal cavities in 3C silicon carbide thin films with mode volumes of less than (lambda/n)^3 and Q's as high as 1,500 with integrated Ky5 defects. Additionally, we performed simulations and analysis of the fabricated structures using observed structural imperfections to determine that the Q's are likely limited primarily by the non-vertical structure sidewall angle. Despite the modest Q's of these structures, they can be utilized to generate large local field intensities to enhance optical interactions with Ky5 qubit states within the cavities. We accomplish this by performing cavity enhanced photoluminescence excitation spectroscopy on cavity modes tuned to the zero phonon line of the defects and observe large (as high as 30 times) increases in the luminescence and optically detected magnetic resonance signals originating from the defect states and approximately 2x faster rates of ground state spin initialization. In addition, we use these techniques to probe the photoluminescence dynamics of the Ky5 defects' optical pumping cycle, perform excitation wavelength dependent studies of spin and spectral inhomogeneity, and use the small mode volume and narrowband photoluminescence enhancements of the cavities to observe spectrally distinct subensembles of defects with linewidths as narrow as 25 GHz within the inhomogeneously broadened zero phonon line. Although much is still unknown regarding the properties of these defects, they show great promise as a candidate system for defect qubit based quantum devices and technologies.
Optically active spins in solid-state systems can be engineered to emit photons that are entangled with the spin in the solid. This allows for applications such as quantum communications, quantum key distribution, and distributed quantum computing. Recently, there has been a strong interest in silicon carbide defects, as they emit very close to the telecommunication wavelength, making them excellent candidates for long range quantum communications. In this work we develop explicit schemes for spin-photon entanglement in several SiC defects: the silicon monovacancy, the silicon divacancy, and the NV center in SiC. Distinct approaches are given for (i) single-photon and spin entanglement and (ii) the generation of long strings of entangled photons. The latter are known as cluster states and comprise a resource for measurement-based quantum information processing.