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arXiv:2210.00076

Correlated twin-photon generation in a silicon nitrite loaded thin film PPLN waveguide

Antoine Henry, David Barral, Isabelle Zaquine, Andreas Boes, Arnan Mitchell, Nadia Belabas, Kamel Bencheikh

Published Sep 30, 2022• 1 citation
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Abstract

Photon-pair sources based on thin film lithium niobate on insulator technology have a great potential for integrated optical quantum information processing. We report on such a source of correlated twin-photon pairs generated by spontaneous parametric down conversion in a silicon nitride (SiN) rib loaded thin film periodically poled lithium niobate (LN) waveguide. The generated photon pairs have a wavelength centred at 1560\,nm compatible with present telecom infrastructure, a large bandwidth (21\,THz) and a brightness of $\sim 2.5\times 10^5$\,pairs/s/mW/GHz. The photons are correlated and exhibit a cross correlation $g^{(2)}(0)$ of about 8000. Using the Hanbury Brown and Twiss effect, we have also shown heralded single photon emission, achieving an autocorrelation $g^{(2)}_H(0) \simeq 0.04$.

DOI
10.48550/arxiv.2210.00076

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Photon-pair sources based on thin film lithium niobate on insulator technology have a great potential for integrated optical quantum information processing. We report on such a source of correlated twin-photon pairs generated by spontaneous parametric down conversion in a silicon nitride (SiN) rib loaded thin film periodically poled lithium niobate (LN) waveguide. The generated correlated photon pairs have a wavelength centred at 1560 nm compatible with present telecom infrastructure, a large bandwidth (21 THz) and a brightness of ∼2.5 × 10 5 pairs/s/mW/GHz. Using the Hanbury Brown and Twiss effect, we have also shown heralded single photon emission, achieving an autocorrelation g H ( 2 ) ( 0 ) ≃ 0.04 .

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quant-pharXiv:2603.09397•Mar 11, 2026•0 citations
Photon-pair sources based on thin film lithium niobate on insulator technology have a great potential for integrated optical quantum information processing. We report on such a source of correlated twin-photon pairs generated by spontaneous parametric down conversion in a silicon nitride (SiN) rib loaded thin film periodically poled lithium niobate (LN) waveguide. The generated photon pairs have a wavelength centred at 1560,nm compatible with present telecom infrastructure, a large bandwidth (21,THz) and a brightness of ∼2.5×105\sim 2.5\times 10^5∼2.5×105,pairs/s/mW/GHz. The photons are correlated and exhibit a cross correlation g(2)(0)g^{(2)}(0)g(2)(0) of about 8000. Using the Hanbury Brown and Twiss effect, we have also shown heralded single photon emission, achieving an autocorrelation gH(2)(0)≃0.04g^{(2)}_H(0) \simeq 0.04gH(2)​(0)≃0.04.
Photon-pair sources based on thin film lithium niobate on insulator technology have a great potential for integrated optical quantum information processing. We report on such a source of correlated twin-photon pairs generated by spontaneous parametric down conversion in a silicon nitride (SiN) rib loaded thin film periodically poled lithium niobate (LN) waveguide. The generated correlated photon pairs have a wavelength centred at 1560 nm compatible with present telecom infrastructure, a large bandwidth (21 THz) and a brightness of ∼2.5 × 10 5 pairs/s/mW/GHz. Using the Hanbury Brown and Twiss effect, we have also shown heralded single photon emission, achieving an autocorrelation g H ( 2 ) ( 0 ) ≃ 0.04 .
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.
on a coarse wavelength-division-multiplexing grid that spans 140 nm by using a 300-μm-long poled region in a thin-film periodically-poled lithium-niobate ridge waveguide bonded to silicon. The pairs are generated via spontaneous parametric downconversion pumped by a continuous-wave tunable laser source. The small mode area of the waveguide allows for efficient interaction in a short length of the waveguide and, as a result, permits photon-pair generation over a broad range of signal-idler wavelengths.
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.
A thin-film periodically poled lithium niobate waveguide was designed and fabricated which generates entangled photon pairs at telecommunications wavelengths with high coincidences-to-accidentals counts ratio CAR>67000, two-photon interference visibility V>99%, and heralded single-photon autocorrelation g_{H}^{(2)}(0)<0.025. Nondestructive in situ diagnostics were used to determine the poling quality in 3D. Megahertz rates of photon pairs were generated by less than a milliwatt of pump power, simplifying the pump requirements and dissipation compared to traditional spontaneous parametric down-conversion lithium niobate devices.
Quantum networks based on wavelength-multiplexed entanglement enable parallel distribution of quantum correlations, increasing channel capacity for secure communication and distributed quantum information processing. However, broadband integrated sources capable of generating multipartite entanglement beyond photon pairs remain scarce. Here we report on-chip generation of telecom-band four-photon entanglement in a periodically poled thin-film lithium niobate on insulator (LNOI) waveguide. Type-0 spontaneous parametric down-conversion provides a phase-matching bandwidth exceeding 200 nm, enabling spectrally separable generation of multi-photon entanglement across the telecom band. The generated photons are encoded in time bins for robust fiber compatibility, and a coherent interface enabling reversible conversion between time-bin and polarization degrees of freedom allows complete quantum state tomography. We measure two-photon entanglement with a brightness of 6.7 MHz/mW/nm and a fidelity of 0.874±0.0020.874 \pm 0.0020.874±0.002. At a pump power of 0.08 mW, the four-photon state exhibits a fourfold coincidence rate of 1 Hz and a fidelity of 0.74±0.010.74 \pm 0.010.74±0.01, representing a threefold improvement over previous integrated platforms. Our results establish LNOI as a scalable platform for broadband multi-photon entanglement and provide a practical route toward dense wavelength-multiplexed quantum networks.