Postselection-loophole-free Bell test under strict spacetime constraints
Abstract
Entanglement gives rise to correlations between distant quantum systems that cannot be explained by local realistic theories. Bell inequality violations provide a direct way to reveal these correlations and certify nonlocality, especially when the relevant experimental loopholes are closed. Time-bin encoding, in which quantum information is encoded into well-defined temporal modes, is a commonly used platform for distributing photonic entanglement in optical fibers. Yet loophole-free Bell tests with time-bin entanglement have received comparatively little attention, owing in part to the postselection loophole introduced by conventional interferometric measurements. Here, we demonstrate a fiber-based platform for Bell tests with time-bin entanglement that simultaneously closes the locality, freedom-of-choice, and postselection loopholes. We observe a CHSH violation of S=2.583 ± 0.002, exceeding the local-realistic bound by over 265 standard deviations. Notably, this rigorous certification of nonlocality is achieved at a separation distance of 49.0 ± 0.7 m, substantially shorter than previous photonic Bell tests addressing comparable space-time constraints. Beyond its foundational significance, our results demonstrate time-bin entanglement as a viable route towards practical device-independent quantum communication and a future quantum internet.
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BibTeX
@misc{vijayadharan2026postselectionloopholefree,
title = {{Postselection-loophole-free Bell test under strict spacetime constraints}},
author = {Kannan Vijayadharan and Matías Rubén Bolaños and Andrea Pompermaier and Tommaso Bertapelle and Francesco B. L. Santagiustina and Costantino Agnesi and Giuseppe Vallone and Paolo Villoresi},
howpublished = {arXiv},
year = {2026},
month = aug,
doi = {10.48550/arxiv.2608.28190},
eprint = {2608.28190},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.28190},
}
RIS
TY - UNPB
TI - Postselection-loophole-free Bell test under strict spacetime constraints
AU - Kannan Vijayadharan
AU - Matías Rubén Bolaños
AU - Andrea Pompermaier
AU - Tommaso Bertapelle
AU - Francesco B. L. Santagiustina
AU - Costantino Agnesi
AU - Giuseppe Vallone
AU - Paolo Villoresi
PY - 2026
DA - 2026/08/28
PB - arXiv
DO - 10.48550/arxiv.2608.28190
UR - https://arxiv.org/abs/2608.28190
AB - Entanglement gives rise to correlations between distant quantum systems that cannot be explained by local realistic theories. Bell inequality violations provide a direct way to reveal these correlations and certify nonlocality, especially when the relevant experimental loopholes are closed. Time-bin encoding, in which quantum information is encoded into well-defined temporal modes, is a commonly used platform for distributing photonic entanglement in optical fibers. Yet loophole-free Bell tests with time-bin entanglement have received comparatively little attention, owing in part to the postselection loophole introduced by conventional interferometric measurements. Here, we demonstrate a fiber-based platform for Bell tests with time-bin entanglement that simultaneously closes the locality, freedom-of-choice, and postselection loopholes. We observe a CHSH violation of S=2.583 ± 0.002, exceeding the local-realistic bound by over 265 standard deviations. Notably, this rigorous certification of nonlocality is achieved at a separation distance of 49.0 ± 0.7 m, substantially shorter than previous photonic Bell tests addressing comparable space-time constraints. Beyond its foundational significance, our results demonstrate time-bin entanglement as a viable route towards practical device-independent quantum communication and a future quantum internet.
ER -