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arXiv:2606.01657

Quantum light source with lithium tantalate for scalable photonic quantum circuits

Yun-Ru Fan, Bo-Wen Chen, Dan Xu, Cheng-Li Wang, Hong Zeng, Jia-Qi Wang, Xu-Qiang Wang, Jia-Chen Cai, Hai-Zhi Song, Hao Li, Li-Xing You, Yan-Yu Wei, Kai Guo, Xin Ou, Guang-Can Guo, Qiang Zhou

quant-phSubmitted Jun 1, 2026• Announced Jun 2, 2026• 0 citations
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Abstract

Thin-film lithium tantalate (TFLT) has emerged as a promising integrated photonic platform owing to its low photorefractive noise, high optical damage threshold, and reduced birefringence, attracting increasing interest for scalable photonic technologies. Here, to the best of our knowledge, we demonstrate the first quantum light source with TFLT via spontaneous four-wave mixing, bridging the gap between the rapidly advancing classical TFLT ecosystem and integrated quantum photonics. The fabricated microring exhibits a free spectral range of 350~GHz and an optical quality factor of $10^6$, enabling efficient cavity-enhanced nonlinear interactions. Correlated photon pairs are generated across the telecom band from 1510 to 1570~nm, with a photon pair generation rate of 24 $\mathrm{MHz/mW^{2}}$ at a wavelength of 1535.04 nm. The source delivers strongly antibunched heralded single photons with $g^{(2)}_{H}(0)=0.071\pm0.004$ at a heralding rate of 170 kHz, while the unheralded statistics yield $g^{(2)}(0)=1.93 \pm 0.05$, indicating near-single-temporal-mode emission. Energy-time entanglement is further confirmed by a raw two-photon interference visibility of $92.55\pm0.94\%$, well above the Bell-inequality violation threshold. These results establish TFLT as a manufacturing-compatible platform for scalable photonic quantum circuits, paving the way for the monolithic co-integration of classical and quantum photonic functionalities.

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Thin-film lithium tantalate (TFLT) has emerged as a promising integrated photonic platform owing to its low photorefractive noise, high optical damage threshold, and reduced birefringence, attracting increasing interest for scalable photonic technologies. Here, to the best of our knowledge, we demonstrate the first quantum light source with TFLT via spontaneous four-wave mixing, bridging the gap between the rapidly advancing classical TFLT ecosystem and integrated quantum photonics. The fabricated microring exhibits a free spectral range of 350GHz and an optical quality factor of 10610^6106, enabling efficient cavity-enhanced nonlinear interactions. Correlated photon pairs are generated across the telecom band from 1510 to 1570nm, with a photon pair generation rate of 24 MHz/mW2\mathrm{MHz/mW^{2}}MHz/mW2 at a wavelength of 1535.04 nm. The source delivers strongly antibunched heralded single photons with gH(2)(0)=0.071±0.004g^{(2)}_{H}(0)=0.071\pm0.004gH(2)​(0)=0.071±0.004 at a heralding rate of 170 kHz, while the unheralded statistics yield g(2)(0)=1.93±0.05g^{(2)}(0)=1.93 \pm 0.05g(2)(0)=1.93±0.05, indicating near-single-temporal-mode emission. Energy-time entanglement is further confirmed by a raw two-photon interference visibility of 92.55±0.94%92.55\pm0.94\%92.55±0.94%, well above the Bell-inequality violation threshold. These results establish TFLT as a manufacturing-compatible platform for scalable photonic quantum circuits, paving the way for the monolithic co-integration of classical and quantum photonic functionalities.
Abstract Chip-integrated photon-pair sources based on spontaneous parametric down-conversion (SPDC) have emerged as a promising solution for scalable quantum light generation. Thin-film lithium tantalate (TFLT) is a compelling χ(2)\chi^{(2)}χ(2) platform, combining strong nonlinearity with a high optical-damage threshold, weak photorefractive response, and ferroelectricity that enables quasi-phase matching. However, SPDC-based photon-pair generation on TFLT has not yet been demonstrated. Here, we combine high-quality periodic poling with low-loss nanophotonic waveguides to realize photon-pair sources on TFLT in both traveling-wave and resonant configurations. In periodically poled straight waveguides, we achieve broadband photon-pair generation with high efficiency (2.1~GHz~mW−1^{-1}−1) and coincidence-to-accidental ratio (up to 3.8×1053.8\times10^{5}3.8×105). We further confirm high-purity single-photon operation via heralded second-order correlation (gH(2)(0)=0.0018±0.0002g^{(2)}_\mathrm{H}(0) = 0.0018 \pm 0.0002gH(2)​(0)=0.0018±0.0002) and high-fidelity time-energy entanglement through Franson interference (visibility of 98.9±0.5%98.9 \pm 0.5\%98.9±0.5%). In periodically poled racetrack resonators, we map out a broad quantum frequency comb spanning the telecom C- and L-bands. By isolating individual frequency-correlated pairs, we measure a high spectral brightness of 11~GHz~mW−1^{-1}−1~GHz−1^{-1}−1. These results are competitive with the state of the art across χ(2)\chi^{(2)}χ(2) integrated platforms, positioning TFLT as a strong contender for integrated quantum light sources, with applications in wavelength-multiplexed quantum communications and photonic quantum information processing.
Chip-integrated photon-pair sources based on spontaneous parametric down-conversion (SPDC) have emerged as a promising solution for scalable quantum light generation. Thin-film lithium tantalate (TFLT) is a compelling χ(2)χ^{(2)}χ(2) platform, combining strong nonlinearity with a high optical-damage threshold, weak photorefractive response, and ferroelectricity that enables quasi-phase matching. However, SPDC-based photon-pair generation on TFLT has not yet been demonstrated. Here, we combine high-quality periodic poling with low-loss nanophotonic waveguides to realize photon-pair sources on TFLT in both traveling-wave and resonant configurations. In periodically poled straight waveguides, we achieve broadband photon-pair generation with high efficiency (2.1 GHz mW−12.1~\mathrm{GHz}~\mathrm{mW}^{-1}2.1 GHz mW−1) and coincidence-to-accidental ratio (up to 3.8×1053.8\times10^{5}3.8×105). We further confirm high-purity single-photon operation via heralded second-order correlation (gH(2)(0)=0.0018±0.0002g^{(2)}_\mathrm{H}(0) = 0.0018 \pm 0.0002gH(2)​(0)=0.0018±0.0002) and high-fidelity time-energy entanglement through Franson interference (visibility of 98.9±0.5%98.9 \pm 0.5\%98.9±0.5%). In periodically poled racetrack resonators, we map out a broad quantum frequency comb spanning the telecom C- and L-bands. By isolating individual frequency-correlated pairs, we measure a high spectral brightness of 11 GHz mW−1 GHz−111~\mathrm{GHz}~\mathrm{mW}^{-1}~\mathrm{GHz}^{-1}11 GHz mW−1 GHz−1. These results are competitive with the state of the art across χ(2)χ^{(2)}χ(2) integrated platforms, positioning TFLT as a strong contender for integrated quantum light sources, with applications in wavelength-multiplexed quantum communications and photonic quantum information processing.
Efficient and stable microwave-optical transduction is a key enabling technology for distributed superconducting quantum computing and heterogeneous quantum networks. Electro-optic transducers based on thin-film lithium niobate (TFLN) have shown strong promise, but demonstrations to date have been limited by various factors such as low frequency bias drift, low efficiency, fabrication complexity, and scalability. Here we demonstrate the first integrated electro-optic microwave-optical transducers realized in thin-film lithium tantalate (TFLT), a material platform offering Pockels nonlinearity comparable to TFLN together with improved bias stability and high-power handling. We fabricate superconducting microwave resonators coupled to tunable photonic-molecule optical resonators using wafer-scale deep ultraviolet lithography, offering high-throughput production of hundreds of devices per wafer. Across six devices we observe coherent bidirectional conversion between C-band optical photons and 4.9-5.5 GHz microwave photons, with measured on-chip efficiencies and inferred single-photon coupling rates g_0/2π ~ 1 kHz consistent with theory. Continuous operation over multiple days is achieved using a static bias field with minimal feedback, demonstrating a major operational advantage. We further characterize optical loss statistics, microwave resonator performance, and optically induced added noise under pulsed pumping, finding less than one added photon for 100 microsecond pulses at the highest measured efficiencies. These results establish TFLT as a scalable and robust electro-optic platform for future quantum interconnects and modular quantum processors.
Abstract Scalable quantum networks require high-quality multi-wavelength light sources to enable simultaneous quantum communication among multiple users 1 . However, realizing such sources with high brightness, low noise, and chip-scale integration remains challenging. We demonstrate a high-quality and multi-wavelength quantum light source based on a periodically poled thin-film lithium niobate (TFLN) microring resonator employing spontaneous parametric down-conversion (SPDC) with a 100-GHz free spectral range (FSR), compatible with International Telecommunication Union (ITU) Channel Grid. In our experiment, twelve pairs of non-degenerate photon pairs are generated, exhibiting a photon-pair generation rate (PGR) of 817 MHz/mW, brightness of 1.86 × 10 9 Hz/mW 2 /GHz, and a coincidence-to-accidental ratio (CAR) of 51,829 ± 2204. The source enables predictable single photons with g (2) (0) = 0.015 ± 0.006 and energy-time entanglement with 99.5% raw visibility. Operating at room temperature, telecom wavelengths, and compatible with network channels, this work represents a crucial step toward realistic scalable, integrated quantum photonic networks in the future.
Integrated quantum light source is increasingly desirable in large-scale quantum information processing.~Despite recent remarkable advances, new material platform is constantly being explored for the fully on-chip integration of quantum light generation, active and passive manipulation, and detection. Here, for the first time, we demonstrate a gallium nitride (GaN) microring based quantum light generation in the telecom C-band, which has potential towards the monolithic integration of quantum light source.~In our demonstration, the GaN microring has a free spectral range of 330 GHz and a near-zero anomalous dispersion region of over 100 nm. The generation of energy-time entangled photon pair is demonstrated with a typical raw two-photon interference visibility of 95.5$\pm$6.5%, which is further configured to generate heralded single photon with a typical heralded second-order auto-correlation gH(2)(0)g^{(2)}_{H}(0)gH(2)​(0) of 0.045$\pm$0.001. Our results pave the way for developing chip-scale quantum photonic circuit.