Spin defects in wide band gap semiconductors are a leading contender in various areas of quantum technology. Most notably they have been established as a novel tool for nanoscale sensing and as major hardware for long distance quantum entanglement, necessary for quantum repeater structures [1,2]. I will present the use of spin defects in Silicon Carbide (SiC) for quantum photonics and specifically for spin-photon interfaces [3]. Specifically, I will address the spin properties of the material and the interplay between photon emission and spin memory times. It turns out, that the silicon vacancy in SiC is an excellent compromise between photonic and spin quantum memory properties [4]. Even when incorporated into microscale photonic waveguides the optical transitions retain high quality such that long spin coherence times and almost transform-limited photon emission can be observed simultaneously.
Spin defects in wide band gap semiconductors are a leading contender in various areas of quantum technology. Most notably they have been established as a novel tool for nanoscale sensing and as major hardware for long distance quantum entanglement, necessary for quantum repeater structures [1,2]. I will present the use of spin defects in Silicon Carbide (SiC) for quantum photonics and specifically for spin-photon interfaces [3]. Specifically, I will address the spin properties of the material and the interplay between photon emission and spin memory times. It turns out, that the silicon vacancy in SiC is an excellent compromise between photonic and spin quantum memory properties [4]. Even when incorporated into microscale photonic waveguides the optical transitions retain high quality such that long spin coherence times and almost transform-limited photon emission can be observed simultaneously.
Spin defects in wide band gap semiconductors are a leading contender in various areas of quantum technology. Most notably they have been established as a novel tool for nanoscale sensing and as major hardware for long distance quantum entanglement, necessary for quantum repeater structures [1],[2]. I will present the use of spin defects in Silicon Carbide (SiC) for quantum photonics and specifically for spin-photon interfaces [3]. Specifically, I will address the spin properties of the material and the interplay between photon emission and spin memory times. It turns out, that the silicon vacancy in SiC is an excellent compromise between photonic and spin quantum memory properties [4]. Even when incorporated into microscale photonic waveguides the optical transitions retain high quality such that long spin coherence times and almost transform-limited photon emission can be observed simultaneously.
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.
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.
The conversion between stationary and flying qubits is a pillar of numerous quantum technologies such as distributed quantum computing as well as many quantum internet and networking protocols. These quantum technologies promise to use resources, in particular entanglement, not available to classical devices to accomplish tasks that are difficult or even impossible to realize with classical devices. Applications range from fundamental research to secure communication. Because some of these applications require the generation of entanglement, even over large distances, there is substantial interest in efficient interfaces between flying qubits, usually photons, and a stationary memory. In this thesis, we evaluate key aspects of optical spin-photon interfaces, a class of devices combining a stationary qubit memory (spins) and an interface with flying qubits (photons). We focus on defects in silicon carbide (SiC) in which a transition metal (TM) atom substitutes a silicon (Si) atom in the lattice, so that the energy levels with naturally bound quantum states localized around the defect lie within the band gap of SiC. We highlight two key properties of these defects as stationary-flying interconnects: First, they have favorable spin coherence properties and the pertaining nuclear spin of the TM can be used as a quantum memory. Second, they feature a localized and efficient spin-photon interface via their excited states. Defects where vanadium takes the place of a Si atom even allow for photon emission with frequencies in one of the fiber-optic transmission windows, which support efficient transmission in optical fiber. Our results are readily combined with numerical ab-initio and experimental data, providing intuition and further insight into the underlying physics. Additionally, the theoretical assessments of this thesis bridge the gap between the fundamental characterization of TM defects in SiC and their use as spin-photon interfaces in future experiments and quantum technology applications. For instance, the proposed nuclear-spin preparation protocol and spin control mark the first step towards an all-optically controlled integrated platform for quantum technology with TM defects in SiC.
Quantum communication promises unprecedented capabilities enabled by the transmission of quantum states of light. However, current implementations face severe distance limitations due to photon loss. Silicon carbide (SiC) defects have emerged as a promising quantum device platform, offering strong optical transitions, long spin coherence lifetimes and the opportunity for integration with semiconductor devices. Some defects with optical transitions in the telecom range have been identified, allowing to interface with fiber networks without the need for wavelength conversion. These unique properties make SiC an attractive platform for the implementation of quantum nodes for quantum communication networks. We provide an overview of the most prominent defects in SiC and their implementation in spin-photon interfaces. Furthermore, we model an exemplary, memory-enhanced quantum communication protocol in order to extract the parameters required to surpass a direct point-to-point link performance. Based on these insights, we summarize the key steps required towards the deployment of SiC devices in large-scale quantum communication networks.
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.