Observation of quantum entanglement with top quarks at the ATLAS detector

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Zwalinski, L, Zou, W, Zormpa, O, Zorbas, TG, Zoch, K, Zoccoli, A, Živković, L, Ziolkowski, M, Zinsser, J, Zimine, NI et al (show 90 more authors) , Zhukov, K, Zhuang, X, Zhu, Y, Zhu, J, Zhu, CG, Zhou, Y, Zhou, N, Zhou, H, Zhou, B, Zhong, D, Zheng, Z, Zheng, X, Zheng, K, Zheng, J, Zhemchugov, A, Zhao, Z, Zhao, Y, Zhao, T, Zhao, H, Zhang, Z, Zhang, Y, Zhang, X, Zhang, T, Zhang, S, Zhang, R, Zhang, P, Zhang, L, Zhang, K, Zhang, J, Zhang, DF, Zhai, M, Zerwas, D, Zerradi, S, Zenz, S, Ženiš, T, Zenin, O, Zenger, DT, Zeng, JC, Zeng, H, Zeitnitz, C, Zaplatilek, O, Zanzi, D, Zang, J, Saa, JAZ, Zambito, S, Zakharchuk, N, Zakareishvili, T, Zak, ZK, Zaid, E, Zabinski, B, Zaazoua, M, Yue, L, Yuan, R, Yuan, M, Yu, Y, Yu, C, Young, C, Young, CJS, Younas, S, Yorita, K, Yin, P, Yexley, MR, Yeo, B, Yeletskikh, I, Yeh, Y, Ye, X, Ye, S, Ye, J, Ye, H, Yao, WM, Yang, Z, Yang, Y, Yang, X, Yang, T, Yang, S, Yang, HT, Yang, HJ, Yan, Z, Yan, S, Yan, J, Yamazaki, Y, Yamazaki, T, Yamauchi, H, Yamashita, E, Yamaguchi, Y, Yacoob, S, Yabsley, B, Xu, Z, Xu, Y and Xu, T (2024) Observation of quantum entanglement with top quarks at the ATLAS detector Nature, 633 (8030). pp. 542-547. ISSN 0028-0836, 1476-4687

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Abstract

Entanglement is a key feature of quantum mechanics<sup>1–3</sup>, with applications in fields such as metrology, cryptography, quantum information and quantum computation<sup>4–8</sup>. It has been observed in a wide variety of systems and length scales, ranging from the microscopic<sup>9–13</sup> to the macroscopic<sup>14–16</sup>. However, entanglement remains largely unexplored at the highest accessible energy scales. Here we report the highest-energy observation of entanglement, in top–antitop quark events produced at the Large Hadron Collider, using a proton–proton collision dataset with a centre-of-mass energy of √s = 13 TeV and an integrated luminosity of 140 inverse femtobarns (fb)<sup>−1</sup> recorded with the ATLAS experiment. Spin entanglement is detected from the measurement of a single observable D, inferred from the angle between the charged leptons in their parent top- and antitop-quark rest frames. The observable is measured in a narrow interval around the top–antitop quark production threshold, at which the entanglement detection is expected to be significant. It is reported in a fiducial phase space defined with stable particles to minimize the uncertainties that stem from the limitations of the Monte Carlo event generators and the parton shower model in modelling top-quark pair production. The entanglement marker is measured to be D = −0.537 ± 0.002 (stat.) ± 0.019 (syst.) for 340GeV<m<inf>tt¯</inf><380GeV. The observed result is more than five standard deviations from a scenario without entanglement and hence constitutes the first observation of entanglement in a pair of quarks and the highest-energy observation of entanglement so far.

Item Type:	Article
Uncontrolled Keywords:	ATLAS Collaboration
Divisions:	Faculty of Science & Engineering Faculty of Science & Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	28 Oct 2024 09:52
Last Modified:	22 Jan 2026 08:46
DOI:	10.1038/s41586-024-07824-z
Open Access URL:	https://www.nature.com/articles/s41586-024-07824-z
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3186262
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