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arXiv:2605.18124

Integrated time-bin entangled quantum light source on a 4H-SiC microring chip

Hong Zeng, Bing-Cheng Yang, Yun-Ru Fan, Li-Ping Zhou, Cheng-Li Wang, Bo-Wen Chen, Ai-Lun Yi, Yong Geng, Guang-Wei Deng, You Wang, Hai-Zhi Song, Jun-Tao Zhang, Hao Li, Li-Xing You, Zi-Hao Zhan, Kai Guo, Xin Ou, Guang-Can Guo, Qiang Zhou

quant-phSubmitted May 18, 2026• Announced May 19, 2026• 0 citations
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Abstract

Integrated time-bin-entangled photon-pair source with cavity-enhanced nonlinear optical processes is essential for quantum information technologies. However, microcavities with a high quality factor inherently introduce a trade-off between generation efficiency and photon bandwidth, which hinders the development of high-speed quantum networks with an integrated source. Here, we address this challenge by optimizing the nonlinearity property of the material and the geometry of the integrated microring resonator with a 4H-silicon carbide platform. Operating at a loaded quality factor of 1.9 $\times$ 10^5 - spectral bandwidth of 1.0 GHz and pumped with 300-ps double pulses separated by 1.25 ns at a repetition rate of 160 MHz, the device achieves a time-bin-entangled photon-pair generation rate of 1.35 $\times$ 10^7 s^-1 mW^-2. A raw visibility of 95.55 $\pm$ 0.18% is measured, showing a violation of Bell's inequality by more than 138 standard deviations, and a fidelity of 94.37 $\pm$ 0.22% is obtained by quantum state tomography. These results provide a scalable pathway to an efficient and broadband time-bin entangled quantum light source, overcoming intrinsic limitations of cavity-based designs and advancing integrated platforms for future quantum communication networks.

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Integrated time-bin-entangled photon-pair source with cavity-enhanced nonlinear optical processes is essential for quantum information technologies. However, microcavities with a high quality factor inherently introduce a trade-off between generation efficiency and photon bandwidth, which hinders the development of high-speed quantum networks with an integrated source. Here, we address this challenge by optimizing the nonlinearity property of the material and the geometry of the integrated microring resonator with a 4H-silicon carbide platform. Operating at a loaded quality factor of 1.9 ×\times× 10^5 - spectral bandwidth of 1.0 GHz and pumped with 300-ps double pulses separated by 1.25 ns at a repetition rate of 160 MHz, the device achieves a time-bin-entangled photon-pair generation rate of 1.35 ×\times× 10^7 s^-1 mW^-2. A raw visibility of 95.55 ±\pm± 0.18% is measured, showing a violation of Bell's inequality by more than 138 standard deviations, and a fidelity of 94.37 ±\pm± 0.22% is obtained by quantum state tomography. These results provide a scalable pathway to an efficient and broadband time-bin entangled quantum light source, overcoming intrinsic limitations of cavity-based designs and advancing integrated platforms for future quantum communication networks.
ABSTRACT Integrated time‐bin‐entangled photon‐pair source with cavity‐enhanced nonlinear optical processes is essential for quantum information technologies. However, microcavities with a high quality factor inherently introduce a trade‐off between generation efficiency and photon bandwidth, which hinders the development of high‐speed quantum networks with an integrated source. Here, we address this challenge by optimizing the nonlinearity property of the material and the geometry of the integrated microring resonator with a 4H‐silicon carbide platform. Operating at a loaded quality factor of ‐ spectral bandwidth of and pumped with 300‐ps double pulses separated by 1.25 ns at a repetition rate of , the device achieves a time‐bin‐entangled photon‐pair generation rate of . A raw visibility of is measured, showing a violation of Bell's inequality by more than 138 standard deviations, and a fidelity of is obtained by quantum state tomography. These results provide a scalable pathway to an efficient and broadband time‐bin entangled quantum light source, overcoming intrinsic limitations of cavity‐based designs and advancing integrated platforms for future quantum communication networks.
Abstract Entanglement plays a vital role in quantum information processing. Owing to its unique material properties, silicon carbide recently emerged as a promising candidate for the scalable implementation of advanced quantum information processing capabilities. To date, however, only entanglement of nuclear spins has been reported in silicon carbide, while an entangled photon source, whether it is based on bulk or chip-scale technologies, remains elusive. Here, we report the demonstration of an entangled photon source in an integrated silicon carbide platform for the first time. Specifically, strongly correlated photon pairs are efficiently generated at the telecom C-band wavelength through implementing spontaneous four-wave mixing in a compact microring resonator in the 4H-silicon-carbide-on-insulator platform. The maximum coincidence-to-accidental ratio exceeds 600 at a pump power of 0.17 mW, corresponding to a pair generation rate of 9×10 3 pairs/s. Energy-time entanglement is created and verified for such signal-idler photon pairs, with the two-photon interference fringes exhibiting a visibility larger than 99%. The heralded single-photon properties are also measured, with the heralded g (2) (0)on the order of 10 -3 , demonstrating the SiC platform as a prospective fully integrated, CMOS-compatible single-photon source for quantum applications.
Abstract Integrated photonics has recently become a leading platform for the realization and processing of optical entangled quantum states in compact, robust, and scalable chip formats with applications in long-distance quantum-secured communication, quantum-accelerated information processing, and non-classical metrology. However, the quantum light sources developed so far have relied on external bulky excitation lasers making them impractical, not reproducible prototype devices, hindering scalability and the transfer out of the lab into real-world applications. Here we demonstrate a fully integrated quantum light source, which overcomes these challenges through the combined integration of a laser cavity, a highly efficient tunable noise suppression filter (> 55 dB) exploiting the Vernier effect, and a nonlinear microring for entangled photon pair generation through spontaneous four-wave mixing. The hybrid quantum source employs an electrically-pumped InP gain section and a Si₃N₄ low-loss microring filter system and demonstrates high-performance parameters, i.e., a pair emission over four resonant modes in the telecom band (bandwidth ∼ 1 THz), and a remarkable pair detection rate of ∼ 620 Hz at a high coincidence-to-accidental ratio of ∼80. The source directly creates high-dimensional frequency-bin entangled quantum states (qubits/qudits), verified by quantum interference measurements with visibilities up to 96% (violating Bell-inequality) and by density matrix reconstruction through state tomography showing fidelities of up to 99%. Our approach, leveraging a hybrid photonic platform, enables commercial-viable, low-cost, compact, light-weight, and field-deployable entangled quantum sources, quintessential for practical, out-of-lab applications, e.g., in quantum processors and quantum satellite communications systems.
4H silicon carbide, as a silicon-based nonlinear optical material platform, exhibits a large bandgap energy, a wide transparent window and moderate second- and third-order optical nonlinearities. The availability of chip-based visible-wavelength nonlinear and quantum light sources pave the way for quantum communications as well as bio-, atomic-, and molecular-related nonlinear and quantum photonic devices and applications on a chip. Microring resonators on the 4H-SiC- on-insulator platform are ideal for efficiently generating nonlinear and quantum light sources integrated with large-scale photonic integrated circuits. In this work, we report our progress in demonstrating such quantum light sources in the visible/near-infrared wavelengths through spontaneous parametric down-conversion in 4H-SiCOI microring resonators utilizing the type-II phase matching.
Abstract Entanglement plays a vital role in quantum information processing. Owing to its unique material properties, silicon carbide recently emerged as a promising candidate for the scalable implementation of advanced quantum information processing capabilities. To date, however, only entanglement of nuclear spins has been reported in silicon carbide, while an entangled photon source, whether it is based on bulk or chip-scale technologies, has remained elusive. Here, we report the demonstration of an entangled photon source in an integrated silicon carbide platform for the first time. Specifically, strongly correlated photon pairs are efficiently generated at the telecom C-band wavelength through implementing spontaneous four-wave mixing in a compact microring resonator in the 4H-silicon-carbide-on-insulator platform. The maximum coincidence-to-accidental ratio exceeds 600 at a pump power of 0.17 mW, corresponding to a pair generation rate of (9 ± 1) × 10 3 pairs/s. Energy-time entanglement is created and verified for such signal-idler photon pairs, with the two-photon interference fringes exhibiting a visibility larger than 99%. The heralded single-photon properties are also measured, with the heralded g (2) (0) on the order of 10 −3 , demonstrating the SiC platform as a prospective fully integrated, complementary metal-oxide-semiconductor compatible single-photon source for quantum applications.
Abstract Silicon carbide (SiC) polytypes are emerging for integrated nonlinear and quantum photonics due to their wide-bandgap energies, second-order optic nonlinearity and process compatibility with complementary metal-oxide-semiconductor technologies. Among polytypes, 3C-SiC is the only one epitaxially grown on wafer-scale silicon substrates. However, on-chip nonlinear and quantum light sources leveraging the second-order nonlinearity of 3C-SiC have not been reported to our knowledge. Here, we design and fabricate an elliptical microring on 3C-SiC. We demonstrate a nonlinear light source with a second-harmonic generation efficiency of 17.4±0.2%W−117.4\pm 0.2 \% {W}^{-1}17.4±0.2%W−1 17.4 ± 0.2 % W − 1 and difference-frequency generation with a signal-idler bandwidth of 97 nm. We demonstrate a spontaneous parametric down-conversion source with a photon-pair generation rate of 4.8 MHz and a coincidence-to-accidental ratio of 3361±843361\pm 843361±84 3361 ± 84 . We measure a low heralded single-photon second-order coherence gH(2)=0.0007{g}_{H}^{\left(2\right)}=0.0007gH(2)​=0.0007 g H 2 = 0.0007 . We observe time-bin entanglement with a visibility of 86.0±2.4%86.0\pm 2.4 \%86.0±2.4% 86.0 ± 2.4 % using this source. Our work paves a way toward SiC-based on-chip nonlinear and quantum photonic circuits.