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arXiv:2509.16049 · Applied Physics Letters

Integrated telecom wavelength heralded single-photon source based on GHz gated detectors

Maria Ana Pereira, Mingsong Wu, Arslan Sajid Raja, Rui Ning Wang, Tobias Jan Kippenberg, Hugo Zbinden, Tiff Brydges, Rob Thew

Published Feb 9, 2026• 1 citation
arXivHTMLPDF

Abstract

We introduce a simple and flexible concept for a heralded—spectrally pure—single-photon source. The scheme uses a probabilistic photon-pair source pumped with a continuous-wave laser, whereby a rapid gating InGaAs/InP single-photon avalanche diode provides a synchronous clock for the system. The low timing jitter of the detector temporally resolves, and hence spectrally filters, the heralded photons. We demonstrate the concept by combining this with a narrow-band integrated silicon nitride photon-pair source. This simple architecture is capable of heralding photons with high spectral purity in the telecom band but could be adapted to other wavelengths and bandwidth regimes.

DOI
10.1063/5.0305411

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We introduce a simple and flexible concept for a heralded—spectrally pure—single-photon source. The scheme uses a probabilistic photon-pair source pumped with a continuous-wave laser, whereby a rapid gating InGaAs/InP single-photon avalanche diode provides a synchronous clock for the system. The low timing jitter of the detector temporally resolves, and hence spectrally filters, the heralded photons. We demonstrate the concept by combining this with a narrow-band integrated silicon nitride photon-pair source. This simple architecture is capable of heralding photons with high spectral purity in the telecom band but could be adapted to other wavelengths and bandwidth regimes.
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We present a pulsed and integrated, highly non-degenerate parametric down-conversion (PDC) source of heralded single photons at telecom wavelengths, paired with heralding photons around 800 nm. The active PDC section is combined with a passive, integrated wavelength division demultiplexer on-chip, which allows for the spatial separation of signal and idler photons with efficiencies of more than 96.5%, as well as with multi-band reflection and anti-reflection coatings which facilitate low incoupling losses and a pump suppression at the output of the device of more than 99%. Our device is capable of preparing single photons with efficiencies of 60% with a coincidences-to-accidentals ratio exceeding 7400. Likewise, it shows practically no significant background noise compared to continuous wave realizations. For low pump powers, we measure a conditioned second-order correlation function of g (2) = 3.8 × 10 −3 , which proves almost pure single-photon generation. In addition, our source can feature a high brightness of 〈 n pulse 〉 = 0.24 generated photon pairs per pump pulse at pump power levels below 100 μ W. The high quality of the pulsed PDC process in conjunction with the integration of highly efficient passive elements makes our device a promising candidate for future quantum networking applications, where an efficient miniaturization plays a crucial role.
We propose silicon nitride (Si3N4\mathrm{S}{\mathrm{i}}_{3}{\mathrm{N}}_{4}Si3​N4​) nanowaveguide-based CMOS-compatible integrated sources of spectrally pure visible-telecom photon pairs. Our designs are intrinsically devoid of spectral correlations, eradicating the need for narrow-band filtering that reduces the source brightness. Further, the signal photons lie in the visible--near-infrared (vis-NIR) band, which can provide increased heralding efficiency of the idler photon in the telecom band using high-efficiency single-photon detectors. For example, a rectangular-cross-section silica-clad Si3N4\mathrm{S}{\mathrm{i}}_{3}{\mathrm{N}}_{4}Si3​N4​ nanowaveguide with dimensions $680\text{~nm}\ifmmode\times\else\texttimes\fi{}840\text{~nm}$ and length 7 cm provides a heralded single-photon purity of approximately $91\mathrm{%}$ for a pump wavelength of 956.8 nm and a pump bandwidth of 1200 GHz, with the signal and idler lying in the visible and telecom bands at approximately 701701701 nm and approximately 150515051505 nm, respectively, demonstrating a peak spectral brightness of approximately $1.2\ifmmode\times\else\texttimes\fi{}{10}^{4}$ photon pairs/s/nm/mW2\mathrm{pairs}/\mathrm{s}/\mathrm{nm}/{\mathrm{mW}}^{2}pairs/s/nm/mW2 for a linear propagation loss of 0.5 dB/cm. The effect of propagation losses on the purity is also studied for such source designs. We also propose some designs capable of generating high-purity photon pairs to address various specific vis-NIR quantum memory transitions with telecom-band interfacing for long-distance hybrid quantum networks. Such compact on-chip sources could have potential applications in various quantum technologies, such as sensing, simulation, computing, communication, and networking.