Observation of quantum entanglement with top quarks at the ATLAS detector.

ATLAS Collaboration (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^1-3, with applications in fields such as metrology, cryptography, quantum information and quantum computation^4-8. It has been observed in a wide variety of systems and length scales, ranging from the microscopic^9-13 to the macroscopic^14-16. 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)^-1 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<mtt¯<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 and Engineering Faculty of Science and Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	28 Oct 2024 09:52
Last Modified:	06 Dec 2024 12:52
DOI:	10.1038/s41586-024-07824-z
Open Access URL:	https://www.nature.com/articles/s41586-024-07824-z
Related URLs:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3186262