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arXiv:1707.02715 · Physical Review Applied

Quantum Properties of Dichroic Silicon Vacancies in Silicon Carbide

Roland Nagy, Matthias Widmann, Matthias Niethammer, Durga Bhaktavatsala Rao Dasari, Ilja Gerhardt, Öney O. Soykal, Marina Radulaski, Takeshi Ohshima, Jelena Vuckovic A, Nguyên Tiên Són, Ivan Gueorguiev Ivanov, Sophia E. Economou, Cristian Bonato, Sang‐Yun Lee, Jörg Wrachtrup

Published Mar 23, 2018• 152 citations
arXivHTMLPDF

Abstract

Semiconductor defects allowing efficient interaction between spins and photons can serve as building blocks for scalable quantum networks. The silicon vacancy (${V}_{\text{Si}}$) in SiC possesses controllable, long-lived ground-state spins, for adjustable fluorescence properties. However, its broad distribution of emitted-photon energies at room temperature means ${V}_{\text{Si}}$'s feasibility needs to be checked at liquid-helium temperature, where phonon coupling is suppressed. This study finds a long spin-coherence time, a doubling in fluorescence intensity by spin control, and 40% photon emission into the zero-phonon line, indicating that ${V}_{\text{Si}}$ in SiC truly is promising for spin-based quantum technology.

DOI
10.1103/physrevapplied.9.034022

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Semiconductor defects allowing efficient interaction between spins and photons can serve as building blocks for scalable quantum networks. The silicon vacancy (VSi{V}_{\text{Si}}VSi​) in SiC possesses controllable, long-lived ground-state spins, for adjustable fluorescence properties. However, its broad distribution of emitted-photon energies at room temperature means VSi{V}_{\text{Si}}VSi​'s feasibility needs to be checked at liquid-helium temperature, where phonon coupling is suppressed. This study finds a long spin-coherence time, a doubling in fluorescence intensity by spin control, and 40% photon emission into the zero-phonon line, indicating that VSi{V}_{\text{Si}}VSi​ in SiC truly is promising for spin-based quantum technology.
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.
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.
The identification of a microscopic configuration of point defects acting as quantum bits is a key step in the advance of quantum information processing and sensing. Among the numerous candidates, silicon-vacancy related centers in silicon carbide (SiC) have shown remarkable properties owing to their particular spin-3/2 ground and excited states. Although, these centers were observed decades ago, two competing models, the isolated negatively charged silicon vacancy and the complex of negatively charged silicon vacancy and neutral carbon vacancy [Phys. Rev. Lett. 115, 247602 (2015)], are still argued as an origin. By means of high-precision first-principles calculations and high-resolution electron spin resonance measurements, we here unambiguously identify the Si-vacancy related qubits in hexagonal SiC as isolated negatively charged silicon vacancies. Moreover, we identify the Si-vacancy qubit configurations that provide room-temperature optical readout.
Solid-state color centers with manipulatable spin qubits and telecom-ranged fluorescence are ideal platforms for quantum communications and distributed quantum computations. In this work, we coherently control the nitrogen-vacancy (NV) center spins in silicon carbide at room temperature, in which telecom-wavelength emission is detected. We increase the NV concentration sixfold through optimization of implantation conditions. Hence, coherent control of NV center spins is achieved at room temperature, and the coherence time T_{2} can be reached to around 17.1 μs. Furthermore, an investigation of fluorescence properties of single NV centers shows that they are room-temperature photostable single-photon sources at telecom range. Taking advantage of technologically mature materials, the experiment demonstrates that the NV centers in silicon carbide are promising platforms for large-scale integrated quantum photonics and long-distance quantum networks.