Decoherence effects in entangled fermion pairs at colliders
Pith reviewed 2026-05-22 19:45 UTC · model grok-4.3
The pith
Radiation decoherence in entangled top-quark pairs at colliders is captured by mapping Kraus operators to integrated Altarelli-Parisi splitting functions.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The effects of radiation on a maximally entangled pair of fermions in a Bell state can be modeled as an open quantum system in which the Kraus operators that govern the system's evolution are identified with the integrated Altarelli-Parisi splitting functions.
What carries the argument
Identification of the Kraus operators for the open-system evolution of the Bell-state fermion pair with the integrated Altarelli-Parisi splitting functions.
If this is right
- Different radiation processes (gluon emission, photon emission, etc.) produce quantitatively different reductions in the entanglement measure.
- The model supplies a concrete, process-dependent correction factor that can be folded into existing spin-correlation analyses at colliders.
- The same mapping supplies a way to predict the scale at which entanglement visibility drops below a detectable threshold as a function of radiated energy.
Where Pith is reading between the lines
- The same identification may extend to other entangled particle pairs produced in high-energy collisions once appropriate splitting functions are substituted.
- Including next-to-leading-order splitting or interference terms could reveal whether the leading-order Kraus map remains a good approximation or requires refinement.
- Experimental programs could test the prediction by binning entanglement measures in events with varying amounts of additional radiation.
Load-bearing premise
The decoherence induced by radiation on the entangled fermion pair can be fully captured by identifying Kraus operators with integrated Altarelli-Parisi splitting functions without additional collider-specific kinematic corrections or higher-order interference terms.
What would settle it
A precision measurement of spin correlations in ttbar events at the LHC that compares the observed entanglement witness with and without the radiation-induced Kraus correction and finds a statistically significant mismatch.
Figures
read the original abstract
Recent measurements at the Large Hadron Collider have observed entanglement in the spins of $t\bar t$ pairs. The effects of radiation, which are expected to lead to quantum decoherence and a reduction of entanglement, are generally neglected in such measurements. In this work we calculate the effects of decoherence from various different types of radiation for a maximally entangled pair of fermions -- a bipartite system of qubits in a Bell state. We identify the Kraus operators describing the evolution of the open quantum system with the integrated Altarelli-Parisi splitting functions.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper claims to calculate the effects of radiation-induced decoherence on maximally entangled fermion pairs (a bipartite qubit system in a Bell state) at colliders such as the LHC, where ttbar spin entanglement has been measured. It proposes to identify the Kraus operators governing the open quantum system evolution directly with the integrated Altarelli-Parisi splitting functions for the relevant parton splittings.
Significance. If the proposed mapping holds after proper derivation, the result would supply a concrete, collider-physics-grounded channel for incorporating decoherence into entanglement observables, addressing an effect that is currently neglected in LHC analyses of top-quark spin correlations.
major comments (1)
- [Abstract] Abstract: the central claim equates the Kraus operators of the open-system channel to the integrated Altarelli-Parisi splitting functions P_{q→q}(z) and P_{q→g}(z) for a Bell state, yet supplies no derivation from the interaction Hamiltonian, no explicit partial trace over radiation degrees of freedom, and no demonstration that spin-dependent helicity amplitudes and joint phase-space measures leave no residual off-diagonal coherences after tracing. This identification is load-bearing for the entire result.
minor comments (1)
- [Abstract] The abstract refers to 'various different types of radiation' without enumerating which emissions (collinear, soft, non-collinear) are treated or how their contributions are combined.
Simulated Author's Rebuttal
We thank the referee for the careful reading of the manuscript and for recognizing the potential significance of incorporating radiation-induced decoherence into collider studies of top-quark spin entanglement. We address the major comment below and commit to revisions that will strengthen the presentation of the central mapping.
read point-by-point responses
-
Referee: [Abstract] Abstract: the central claim equates the Kraus operators of the open-system channel to the integrated Altarelli-Parisi splitting functions P_{q→q}(z) and P_{q→g}(z) for a Bell state, yet supplies no derivation from the interaction Hamiltonian, no explicit partial trace over radiation degrees of freedom, and no demonstration that spin-dependent helicity amplitudes and joint phase-space measures leave no residual off-diagonal coherences after tracing. This identification is load-bearing for the entire result.
Authors: We agree that the abstract states the identification concisely without reproducing the full technical steps. The manuscript motivates the mapping by noting that the integrated splitting functions encode the probability of emitting radiation carrying away momentum fraction z, which entangles the fermion spin with the unobserved radiation degrees of freedom; tracing over the latter then yields an effective channel on the spin qubits. To make this rigorous and address the referee’s valid concern, the revised manuscript will include a new dedicated section (or appendix) that begins from the relevant QED/QCD interaction Hamiltonian, computes the spin-dependent helicity amplitudes for the splitting processes, integrates over the radiation phase space with the appropriate joint measures, performs the partial trace explicitly, and demonstrates that residual off-diagonal coherences vanish for the symmetric integration employed. This will establish that the resulting operators are indeed the Kraus operators of a valid decoherence channel. revision: yes
Circularity Check
No circularity: central identification uses external standard results
full rationale
The paper's key step is an identification of Kraus operators for the open-system decoherence channel with integrated Altarelli-Parisi splitting functions, which are established QCD results external to this work. No equation or claim reduces by construction to a quantity fitted inside the paper, a self-definition, or a load-bearing self-citation chain. The derivation applies standard open-quantum-system formalism to a Bell state and imports the splitting functions as inputs rather than deriving them from the target entanglement observables, leaving the central claim independent of its own outputs.
Axiom & Free-Parameter Ledger
axioms (1)
- domain assumption Radiation processes can be modeled as the environment causing decoherence in the open quantum system of the entangled fermion pair.
Forward citations
Cited by 4 Pith papers
-
Automated computation of spin-density matrices and quantum observables for collider physics
An automated framework in MadGraph5_aMC@NLO computes tree-level production spin-density matrices and quantum observables for generic collider processes, with validation on ttbar and VV and new applications to multi-to...
-
Radiation effects on the entanglement of fermion pairs at colliders
Energetic radiation induces decoherence that significantly reduces entanglement in fermion pairs at colliders, with statistically significant signals observable in ttbar(g) at the LHC and tau pairs at Belle II.
-
Spin Correlation and Quantum Entanglement of Fermion Pairs in Transversely Polarized $e^-e^+$ Collisions
Transverse polarization in e+e- collisions generates maximally entangled fermion pairs in QED processes and boosts entanglement in electroweak and Bhabha scattering.
-
Understanding Bell locality tests at colliders
Under mild assumptions, local hidden variable theories become testable at colliders and can be disproved via Bell-like inequalities for muon and tau pairs.
Reference graph
Works this paper leans on
-
[1]
Parti- cle Theory at the Higgs Centre
R.A. is supported by UK Research and In- novation (UKRI) under the UK government’s Hori- zon Europe Marie Sklodowska-Curie funding guarantee grant [EP/Z000947/1] and by the STFC grant “Parti- cle Theory at the Higgs Centre”. The work of AJB is funded in part through STFC grants ST/R002444/1 and ST/S000933/1. F.M. is partially supported by the PRIN2022 Gra...
-
[2]
R. Horodecki, P. Horodecki, M. Horodecki, and K. Horodecki, Rev. Mod. Phys. 81, 865 (2009), arXiv:quant-ph/0702225
work page internal anchor Pith review Pith/arXiv arXiv 2009
-
[3]
Entanglement and quantum tomography with top quarks at the LHC,
Y. Afik and J. R. M. n. de Nova, Eur. Phys. J. Plus 136, 907 (2021), arXiv:2003.02280 [quant-ph]
-
[4]
Quantum tops at the LHC: from entanglement to Bell inequalities,
C. Severi, C. D. E. Boschi, F. Maltoni, and M. Sioli, Eur. Phys. J. C 82, 285 (2022), arXiv:2110.10112 [hep-ph]
-
[5]
Quantum SMEFT tomography: Top quark pair pro- duction at the LHC,
R. Aoude, E. Madge, F. Maltoni, and L. Mantani, Phys. Rev. D 106, 055007 (2022), arXiv:2203.05619 [hep-ph]
-
[6]
Y. Afik and J. R. M. n. de Nova, Quantum 6, 820 (2022), arXiv:2203.05582 [quant-ph]
-
[7]
Y. Afik and J. R. M. n. de Nova, Phys. Rev. Lett. 130, 221801 (2023), arXiv:2209.03969 [quant-ph]
- [8]
-
[9]
Quantum entanglement and top spin correlations in SMEFT at higher orders,
C. Severi and E. Vryonidou, JHEP 01, 148 (2023), arXiv:2210.09330 [hep-ph]
-
[10]
R. Ashby-Pickering, A. J. Barr, and A. Wierzchucka, JHEP 05, 020 (2023), arXiv:2209.13990 [quant-ph]
-
[11]
Con- straining new physics in entangled two-qubit systems: top-quark, tau-lepton and photon pairs,
M. Fabbrichesi, R. Floreanini, and E. Gabrielli, Eur. Phys. J. C 83, 162 (2023), arXiv:2208.11723 [hep-ph]
- [12]
- [13]
- [14]
-
[15]
M. Fabbrichesi, R. Floreanini, E. Gabrielli, and L. Mar- zola, Eur. Phys. J. C 83, 823 (2023), arXiv:2302.00683 [hep-ph]
-
[16]
K. Sakurai and M. Spannowsky, Phys. Rev. Lett. 132, 151602 (2024), arXiv:2310.01477 [quant-ph]
-
[17]
C. Altomonte and A. J. Barr, Phys. Lett. B 847, 138303 (2023), arXiv:2312.02242 [hep-ph]. 6
- [18]
-
[19]
Grabarczyk, (2024), arXiv:2410.18022 [hep-ph]
R. Grabarczyk, (2024), arXiv:2410.18022 [hep-ph]
- [20]
- [21]
-
[22]
C. Altomonte, A. J. Barr, M. Eckstein, P. Horodecki, and K. Sakurai, (2024), arXiv:2412.01892 [hep-ph]
- [23]
- [24]
- [25]
-
[26]
Observation of quantum entanglement in top-quark pairs using the ATLAS detector,
G. Aad et al. (ATLAS), Nature 633, 542 (2024), arXiv:2311.07288 [hep-ex]
-
[27]
A. Hayrapetyan et al. (CMS), Rept. Prog. Phys. 87, 117801 (2024), arXiv:2406.03976 [hep-ex]
-
[28]
A. Hayrapetyan et al. (CMS), (2024), arXiv:2409.11067 [hep-ex]
-
[29]
A. Behring, M. Czakon, A. Mitov, A. S. Papanastasiou, and R. Poncelet, Phys. Rev. Lett. 123, 082001 (2019), arXiv:1901.05407 [hep-ph]
- [30]
-
[31]
J. Mazzitelli, P. F. Monni, P. Nason, E. Re, M. Wiese- mann, and G. Zanderighi, JHEP 04, 079 (2022), arXiv:2112.12135 [hep-ph]
-
[32]
H. D. Zeh, Foundations of Physics 1, 69 (1970)
work page 1970
-
[33]
W. H. Zurek, Phys. Rev. D 24, 1516 (1981)
work page 1981
-
[34]
W. H. Zurek, Phys. Rev. D 26, 1862 (1982)
work page 1982
-
[35]
Environment-induced deco- herence and the transition from quantum to classical,
J. P. Paz and W. H. Zurek, “Environment-induced deco- herence and the transition from quantum to classical,” in Coherent atomic matter waves (Springer Berlin Heidel- berg) p. 533–614
-
[36]
Decoherence and the transition from quantum to classical – revisited,
W. H. Zurek, “Decoherence and the transition from quantum to classical – revisited,” (2003), arXiv:quant- ph/0306072 [quant-ph]
-
[37]
R. A. Bertlmann, Lect. Notes Phys. 689, 1 (2006), arXiv:quant-ph/0410028
work page internal anchor Pith review Pith/arXiv arXiv 2006
- [38]
- [39]
- [40]
-
[41]
D. Carney, L. Chaurette, D. Neuenfeld, and G. W. Semenoff, Phys. Rev. Lett. 119, 180502 (2017), arXiv:1706.03782 [hep-th]
work page internal anchor Pith review Pith/arXiv arXiv 2017
-
[42]
Dressed infrared quantum information
D. Carney, L. Chaurette, D. Neuenfeld, and G. W. Semenoff, Phys. Rev. D 97, 025007 (2018), arXiv:1710.02531 [hep-th]
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[43]
D. Carney, L. Chaurette, D. Neuenfeld, and G. Semenoff, JHEP 09, 121 (2018), arXiv:1803.02370 [hep-th]
work page internal anchor Pith review Pith/arXiv arXiv 2018
-
[44]
Neuenfeld, JHEP 11, 189 (2021), arXiv:1810.11477 [hep-th]
D. Neuenfeld, JHEP 11, 189 (2021), arXiv:1810.11477 [hep-th]
- [45]
-
[46]
M. Schlosshauer, Phys. Rept. 831, 1 (2019), arXiv:1911.06282 [quant-ph]
- [47]
-
[48]
J. C. Collins, Nuclear Physics B 304, 794 (1988)
work page 1988
-
[49]
Knowles, Nuclear Physics B 304, 767 (1988)
I. Knowles, Nuclear Physics B 304, 767 (1988)
work page 1988
-
[50]
Parton showers with quantum interference
Z. Nagy and D. E. Soper, JHEP 09, 114 (2007), arXiv:0706.0017 [hep-ph]
work page internal anchor Pith review Pith/arXiv arXiv 2007
-
[51]
Parton showers with quantum interference: leading color, with spin
Z. Nagy and D. E. Soper, JHEP 07, 025 (2008), arXiv:0805.0216 [hep-ph]
work page internal anchor Pith review Pith/arXiv arXiv 2008
-
[52]
Parton showers with quantum interference: leading color, spin averaged
Z. Nagy and D. E. Soper, JHEP 03, 030 (2008), arXiv:0801.1917 [hep-ph]
work page internal anchor Pith review Pith/arXiv arXiv 2008
-
[53]
Parton shower evolution with subleading color
Z. Nagy and D. E. Soper, JHEP 06, 044 (2012), arXiv:1202.4496 [hep-ph]
work page internal anchor Pith review Pith/arXiv arXiv 2012
-
[54]
Richardson, JHEP 11, 029 (2001), arXiv:hep- ph/0110108
P. Richardson, JHEP 11, 029 (2001), arXiv:hep- ph/0110108
-
[55]
Spin Correlations in Parton Shower Simulations
P. Richardson and S. Webster, Eur. Phys. J. C 80, 83 (2020), arXiv:1807.01955 [hep-ph]
work page internal anchor Pith review Pith/arXiv arXiv 2020
-
[56]
K. Hamilton, A. Karlberg, G. P. Salam, L. Scyboz, and R. Verheyen, JHEP 03, 193 (2022), arXiv:2111.01161 [hep-ph]
-
[57]
T. Kinoshita, Journal of Mathematical Physics 3, 650 (1962), https://pubs.aip.org/aip/jmp/article- pdf/3/4/650/19167464/650 1 online.pdf
work page 1962
-
[58]
T. D. Lee and M. Nauenberg, Phys. Rev. 133, B1549 (1964)
work page 1964
- [59]
- [60]
- [61]
-
[62]
B. A. Kniehl, Nucl. Phys. B 376, 3 (1992)
work page 1992
- [63]
-
[64]
A. Karlberg, G. P. Salam, L. Scyboz, and R. Verheyen, Eur. Phys. J. C 81, 681 (2021), arXiv:2103.16526 [hep- ph]
-
[65]
J. Kublbeck, H. Eck, and R. Mertig, Nucl. Phys. B Proc. Suppl. 29, 204 (1992)
work page 1992
-
[66]
New Developments in FeynCalc 9.0
V. Shtabovenko, R. Mertig, and F. Orellana, Comput. Phys. Commun. 207, 432 (2016), arXiv:1601.01167 [hep- ph]
work page internal anchor Pith review Pith/arXiv arXiv 2016
-
[67]
FeynCalc 9.3: New features and improvements
V. Shtabovenko, R. Mertig, and F. Orellana, Comput. Phys. Commun. 256, 107478 (2020), arXiv:2001.04407 [hep-ph]
work page internal anchor Pith review Pith/arXiv arXiv 2020
- [68]
-
[69]
Decoherence effects in entangled fermion pairs at colliders
F. Maltoni, D. Pagani, and S. Tentori, JHEP 09, 098 (2024), arXiv:2406.06694 [hep-ph]. 1 Supplemental Material for “Decoherence effects in entangled fermion pairs at colliders” Rafael Aoude, Alan J. Barr, Fabio Maltoni and Leonardo Satrioni In this Supplemental Material, we provide details on the calculation of the main body as the explicit coefficients o...
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.