An asymmetric atom-photon architecture for device-independent quantum key distribution over 25 km
Abstract
Device-independent quantum key distribution (DIQKD) can guarantee security without trusting the internal workings of the measurement devices, but extending it to fiber networks demands high-quality entanglement, reliable heralding, and faithful photon transmission simultaneously. Here, we address these requirements in an event-ready asymmetric atom-photon architecture implemented over 25 km of spooled telecom fiber. A single trapped 40Ca+ ion forms one party of the protocol while a single transmitted photon measured at the remote station forms the other. Double quantum frequency conversion and active polarization stabilization preserve the atom-photon quantum correlation across the full link. We obtain a Clauser-Horne-Shimony-Holt parameter of |S|=2.75+0.16−0.15, exceeding the threshold |S|=2.362 required for a positive asymptotic secret-key fraction under the DIQKD model used. Within the same asymptotic model, this corresponds to a conservative estimate of 69 secret-key bits out of 10908 detected Bell states. The demonstrated architecture establishes a route towards DIQKD in heterogeneous, repeater-compatible quantum networks.
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BibTeX
@misc{meiers2026asymmetric,
title = {{An asymmetric atom-photon architecture for device-independent quantum key distribution over 25 km}},
author = {Jonas Meiers and Christian Haen and Max Bergerhoff and Pascal Baumgart and Tobias Bauer and Christoph Becher and Jürgen Eschner},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.25795},
eprint = {2609.25795},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.25795},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - An asymmetric atom-photon architecture for device-independent quantum key distribution over 25 km
AU - Jonas Meiers
AU - Christian Haen
AU - Max Bergerhoff
AU - Pascal Baumgart
AU - Tobias Bauer
AU - Christoph Becher
AU - Jürgen Eschner
PY - 2026
DA - 2026/09/23
PB - arXiv
DO - 10.48550/arxiv.2609.25795
UR - https://arxiv.org/abs/2609.25795
AB - Device-independent quantum key distribution (DIQKD) can guarantee security without trusting the internal workings of the measurement devices, but extending it to fiber networks demands high-quality entanglement, reliable heralding, and faithful photon transmission simultaneously. Here, we address these requirements in an event-ready asymmetric atom-photon architecture implemented over 25 km of spooled telecom fiber. A single trapped ^40Ca^+ ion forms one party of the protocol while a single transmitted photon measured at the remote station forms the other. Double quantum frequency conversion and active polarization stabilization preserve the atom-photon quantum correlation across the full link. We obtain a Clauser-Horne-Shimony-Holt parameter of |S|=2.75^+0.16_−0.15, exceeding the threshold |S|=2.362 required for a positive asymptotic secret-key fraction under the DIQKD model used. Within the same asymptotic model, this corresponds to a conservative estimate of 69 secret-key bits out of 10908 detected Bell states. The demonstrated architecture establishes a route towards DIQKD in heterogeneous, repeater-compatible quantum networks.
ER -