Abstract
Frequency-bin entangled photons can be efficiently produced on-chip which offers a scalable, robust and low-footprint platform for quantum communication, particularly well-suited for resource-constrained settings such as mobile or satellite-based systems. However, analyzing such entangled states typically requires active and lossy components, limiting scalability and multi-mode compatibility. We demonstrate a novel technique for processing frequency-encoded photons using linear interferometry and time-resolved detection. Our approach is fully passive and compatible with spatially multi-mode light, making it suitable for free-space and satellite-to-ground applications. As a proof-of-concept, we utilize frequency-bin entangled photons generated from a high-brightness multi-resonator source integrated on-chip to show the ability to perform arbitrary projective measurements over both single- and multi-mode channels. We report the first measurement of the joint temporal intensity between frequency-bin entangled photons, which allows us to certify entanglement by violating the Clauser-Horne-Shimony-Holt (CHSH) inequality, with a measured value of ∣S∣ = 2.32 ± 0.05 over multi-mode fiber. By combining time-resolved detection with energy-correlation measurements, we perform full quantum state tomography, yielding a state fidelity of up to 91%. We further assess our ability to produce non-classical states via a violation of time-energy entropic uncertainty relations and investigate the feasibility of a quantum key distribution protocol. Our work establishes a resource-efficient and scalable approach toward the deployment of robust frequency-bin entanglement over free-space and satellite-based links.
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Data availability
The analysis code is provided in ref. 61. The data sets used and analyzed in the current study are available from the corresponding author on reasonable request.
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Acknowledgements
The authors thank Micro Photon Devices for kindly providing the MPD PDM-IR detector. The authors thank Kaylee Sherk, Kimia Mohammadi, Paul Godin, Katanya Kuntz, and Giuseppe Vallone for helpful discussions. This work is co-funded by the Natural Sciences and Engineering Research Council of Canada (NSERC) and the European Union (EU) under Grant no. 101070168 (HyperSpace). The authors further acknowledge support from the NRC Quantum Sensing Challenge Program (QSP-019), the Canada Excellence Research Chair program (CERC), the Canadian Foundation for Innovation (CFI), the Ontario Research Fund (ORF), and the Institute for Quantum Computing. S.V. thanks the NSERC CGS-D for personal funding. M.C. and M.B. acknowledge support by the Italian Ministry of Education (MUR) PNRR project PE0000023-NQSTI.
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S.V., Y.Z., M.B., M.Ga., D.B., and T.J. conceived the original idea. M.C. and Y.Z. developed the theoretical framework. M.C. and M.B. developed the frequency-bin entangled photon source. S.V. and M. Gi. engineered and fabricated the field-widened interferometers with the assistance of L.N. S.V., M.C., M.B., and M. Gi. performed the experimental measurements. P.V., M.Ga., D.B., and T.J. supervised the experiment. S.V. performed the data analysis with the assistance of M.C., Y.Z., and M.B. S.V., M.C., and Y.Z. wrote and revised the manuscript. All authors commented on the manuscript.
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Vinet, S., Clementi, M., Bacchi, M. et al. Time-resolved certification of frequency-bin entanglement over multi-mode channels. npj Quantum Inf (2026). https://doi.org/10.1038/s41534-026-01183-5
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DOI: https://doi.org/10.1038/s41534-026-01183-5
