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arXiv · 2508.10200

Time-resolved certification of frequency-bin entanglement over multi-mode channels

Stéphane Vinet·Marco Clementi·Marcello Bacchi·Yujie Zhang·Massimo Giacomin·Luke Neal·Paolo Villoresi·Matteo Galli·Daniele Bajoni·Thomas Jennewein
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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 $|S|=2.32\pm0.05$ 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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Stéphane Vinet, Marco Clementi, Marcello Bacchi, Yujie Zhang, Massimo Giacomin, Luke Neal, Paolo Villoresi, Matteo Galli, Daniele Bajoni, Thomas Jennewein. 2025-08-13. Time-resolved certification of frequency-bin entanglement over multi-mode channels. https://doi.org/10.1038/s41534-026-01183-5

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