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Entanglement Entropy in Quantum Field Theory

A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Quantum Information".

Deadline for manuscript submissions: closed (31 July 2025) | Viewed by 4448

Special Issue Editors


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Guest Editor
Department of Mathematics, City, University of London, London EC1V 0HB, UK
Interests: integrable quantum field theory; entanglement measures; out-of-equilibrium dynamics; form factor programme; TBA

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Guest Editor
Department of Mathematics, King’s College London, London WC2R 2LS, UK
Interests: out-of-equilibrium dynamics of isolated quantum systems; integrable quantum field theory; conformal field theory; truncated Hilbert space methods; cold atom experiments; entanglement and its dynamics in 1 dimensional systems; symmetry-resolved entanglement; the sine-Gordon theory

Special Issue Information

Dear Colleagues,

At the beginning of the 1990s, a series of works involving C. Callan, C. Holzhey, F. Larsen and F. Wilczek highlighted the universal properties of a measure of entanglement known as entanglement entropy. Their studies considered quantum corrections to black hole entropy and saw entropy in the context of geometry and gravity. Those results admitted also a more general interpretation as describing the quantum entanglement associated with quantum critical points, which in 1+1 dimensions are described by the conformal field theory (CFT). Drawing on the powerful mathematical structures underpinning CFT, it has since been possible to obtain many more universal results for a wide range of entanglement measures, ranging from the entanglement and Rényi entropies to the logarithmic negativity. There have been many contributions to this development, with the work of P. Calabrese and J. L. Cardy in 2004 playing a pivotal role in bringing these ideas to the low-dimensional quantum field theory (QFT) community. Later, this CFT viewpoint has been related to a picture emerging from the AdS/CFT correspondence, leading to the well-known relationship between entanglement entropy and the area minimal surfaces pioneered by S. Ryu and T. Takayanagi in 2006. Another frontier in this investigation has been the challenge of progressing beyond CFT, to describing universal properties of entanglement in the near-critical region described by massive QFT. For interacting integrable 1+1-dimensional QFTs, the branch point twist field approach, introduced by J.L. Cardy, O. A. Castro-Alvaredo and B. Doyon in 2007, has become a leading method to do just that. By relating entanglement measures to correlation functions of local fields, it has been possible to encapsulate the intricacies of entanglement measures into the problem of expanding multi-point correlation functions in terms of different parameters. This viewpoint has been further generalised to describe more recent entanglement measures such as the symmetry resolved entanglement, introduced by Goldstein and Sela in 2018, in terms of a composite twist field picture. The objective of this Special Issue is to bring together original contributions to this active area of research.

Dr. Olalla Castro-Alvaredo
Dr. David X. Horvath
Guest Editors

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Keywords

  • entanglement measures
  • quantum field theory
  • conformal field theory
  • quantum spin chains
  • holography
  • symmetry
  • numerics
  • exact results

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Published Papers (4 papers)

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Research

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34 pages, 5443 KB  
Article
Quantum and Topological Dynamics of GKSL Equation in Camel-like Framework
by Sergio Manzetti and Andrei Khrennikov
Entropy 2025, 27(10), 1022; https://doi.org/10.3390/e27101022 - 28 Sep 2025
Viewed by 487
Abstract
We study the dynamics of von Neumann entropy driven by the Gorini–Kossakowski–Sudarshan–Lindblad (GKSL) equation, focusing on its camel-like behavior—a hump-like entropy evolution reflecting the system’s adaptation to its environment. Within this framework, we analyze quantum correlations under decoherence and environmental interaction for three [...] Read more.
We study the dynamics of von Neumann entropy driven by the Gorini–Kossakowski–Sudarshan–Lindblad (GKSL) equation, focusing on its camel-like behavior—a hump-like entropy evolution reflecting the system’s adaptation to its environment. Within this framework, we analyze quantum correlations under decoherence and environmental interaction for three sets of quantum states. Our results show that the sign of the entanglement entropy’s derivative serves as an indicator of the system’s drift toward either classical or quantum information exchange—an insight relevant to quantum error correction and dissipation in quantum thermal machines. We parameterize quantum states using both single-parameter and Bloch-sphere representations, where the angle θ on the Bloch sphere corresponds to the state’s position. On this sphere, we construct gradient and basin maps that partition the dynamics of quantum states into stable and unstable regions under decoherence. Notably, we identify a Braiding ring of decoherence-unstable states located at θ=3π4; these states act as attractors under a constructed Lyapunov function, illustrating the topological and dynamical complexity of quantum evolution. Finally, we propose a testable experimental setup based on camel-like entropy and discuss its connection to the theoretical framework of this entropy behavior. Full article
(This article belongs to the Special Issue Entanglement Entropy in Quantum Field Theory)
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24 pages, 1419 KB  
Article
Measurement-Induced Symmetry Restoration and Quantum Mpemba Effect
by Giuseppe Di Giulio, Xhek Turkeshi and Sara Murciano
Entropy 2025, 27(4), 407; https://doi.org/10.3390/e27040407 - 10 Apr 2025
Cited by 11 | Viewed by 1753
Abstract
Monitoring a quantum system can profoundly alter its dynamical properties, leading to non-trivial emergent phenomena. In this work, we demonstrate that dynamical measurements strongly influence the evolution of symmetry in many-body quantum systems. Specifically, we demonstrate that monitored systems governed by non-Hermitian dynamics [...] Read more.
Monitoring a quantum system can profoundly alter its dynamical properties, leading to non-trivial emergent phenomena. In this work, we demonstrate that dynamical measurements strongly influence the evolution of symmetry in many-body quantum systems. Specifically, we demonstrate that monitored systems governed by non-Hermitian dynamics exhibit a quantum Mpemba effect, where systems with stronger initial asymmetry relax faster to a symmetric state. Crucially, this phenomenon is purely measurement-induced: in the absence of measurements, we find states where the corresponding unitary evolution does not display any Mpemba effect. Furthermore, we uncover a novel measurement-induced symmetry restoration mechanism: below a critical measurement rate, the symmetry remains broken, but beyond a threshold, it is fully restored in the thermodynamic limit—along with the emergence of the quantum Mpemba effect. Full article
(This article belongs to the Special Issue Entanglement Entropy in Quantum Field Theory)
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11 pages, 286 KB  
Article
Entropic Order Parameters for Categorical Symmetries in 2D-CFT
by Javier Molina-Vilaplana, Pablo Saura-Bastida and Germán Sierra
Entropy 2024, 26(12), 1064; https://doi.org/10.3390/e26121064 - 6 Dec 2024
Cited by 1 | Viewed by 895
Abstract
In this work, we propose an information theoretic order parameter able to characterize the presence and breaking of categorical symmetries in (1+1)-d rational conformal field theories (RCFTs). Specifically, we compute the quantum relative entropy between the ground states [...] Read more.
In this work, we propose an information theoretic order parameter able to characterize the presence and breaking of categorical symmetries in (1+1)-d rational conformal field theories (RCFTs). Specifically, we compute the quantum relative entropy between the ground states of RCFTs representing the critical point of phase transitions between different symmetry-broken phases of theories with categorical symmetries, and their symmetrized versions. We find that, at leading order in the high temperature limit, this relative entropy only depends on the expectation values of the quantum dimensions of the topological operators implementing the categorical symmetry. This dependence suggests that our proposal can be used to characterize the different broken phases of (1+1)-d theories with categorical symmetries. Full article
(This article belongs to the Special Issue Entanglement Entropy in Quantum Field Theory)

Review

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104 pages, 2313 KB  
Review
Twist Fields in Many-Body Physics
by Benjamin Doyon
Entropy 2025, 27(12), 1230; https://doi.org/10.3390/e27121230 - 4 Dec 2025
Viewed by 130
Abstract
The notion of twist fields has played a fundamental role in many-body physics. It is used to construct the so-called disorder parameter for the study of phase transitions in the classical Ising model of statistical mechanics, it is involved in the Jordan–Wigner transformation [...] Read more.
The notion of twist fields has played a fundamental role in many-body physics. It is used to construct the so-called disorder parameter for the study of phase transitions in the classical Ising model of statistical mechanics, it is involved in the Jordan–Wigner transformation in quantum chains and bosonisation in quantum field theory, and it is related to measures of entanglement in many-body quantum systems. I provide a pedagogical introduction to the notion of twist field and the concepts at its roots, and review some of its applications, focussing on the 1 + 1 dimension. This includes locality and extensivity, internal symmetries, semi-locality, the standard exponential form and HEGT fields, path-integral defects and Riemann surfaces, topological invariance, and twist families. Additional topics touched upon include renormalisation and form factors in relativistic quantum field theory, tau functions of integrable PDEs, thermodynamic and hydrodynamic principles, and branch-point twist fields for entanglement entropy. One-dimensional quantum systems such as chains (e.g., quantum Heisenberg model) and field theory (e.g., quantum sine-Gordon model) are the main focus, but I also explain how the notion applies to equilibrium statistical mechanics (e.g., classical Ising lattice model), and how some aspects can be adapted to one-dimensional classical dynamical systems (e.g., classical Toda chain). Full article
(This article belongs to the Special Issue Entanglement Entropy in Quantum Field Theory)
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