Bell inequality violation with momentum-entangled massive particles
Abstract
Bell's theorem revealed the fundamental incompatibility between the predictions of quantum mechanics and local realism. Bell inequality violations have since demonstrated quantum nonlocality using photons and internal states of massive particles, but never using their motional states. Here we report the first Bell inequality violation in the motional states of massive particles. Using momentum-entangled pairs of metastable helium atoms manipulated by matter-wave interferometry, we measure a Clauser-Horne-Shimony-Holt (CHSH) Bell parameter of S = 2.52 ± 0.17, violating the CHSH-Bell inequality (S ≤ 2). Our work completes a long-standing objective in quantum atom optics by extending Bell tests from internal quantum variables to the external degrees of freedom of massive particles, opening a new regime for exploring quantum nonlocality in matter waves and for investigating the interplay between quantum mechanics and gravity.
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BibTeX
@misc{athreya2026bell,
title = {{Bell inequality violation with momentum-entangled massive particles}},
author = {Y. S. Athreya and S. Kannan and X. T. Yan and K. V. Kheruntsyan and A. G. Truscott and S. S. Hodgman},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.02009},
eprint = {2609.02009},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.02009},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Bell inequality violation with momentum-entangled massive particles
AU - Y. S. Athreya
AU - S. Kannan
AU - X. T. Yan
AU - K. V. Kheruntsyan
AU - A. G. Truscott
AU - S. S. Hodgman
PY - 2026
DA - 2026/09/02
PB - arXiv
DO - 10.48550/arxiv.2609.02009
UR - https://arxiv.org/abs/2609.02009
AB - Bell's theorem revealed the fundamental incompatibility between the predictions of quantum mechanics and local realism. Bell inequality violations have since demonstrated quantum nonlocality using photons and internal states of massive particles, but never using their motional states. Here we report the first Bell inequality violation in the motional states of massive particles. Using momentum-entangled pairs of metastable helium atoms manipulated by matter-wave interferometry, we measure a Clauser-Horne-Shimony-Holt (CHSH) Bell parameter of S = 2.52 ± 0.17, violating the CHSH-Bell inequality (S ≤ 2). Our work completes a long-standing objective in quantum atom optics by extending Bell tests from internal quantum variables to the external degrees of freedom of massive particles, opening a new regime for exploring quantum nonlocality in matter waves and for investigating the interplay between quantum mechanics and gravity.
ER -