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Entanglement in Quantum Spin Systems

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

Deadline for manuscript submissions: 25 May 2025 | Viewed by 3150

Special Issue Editor


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Guest Editor
Department of Physics, Federal Education Center Technological of Minas Gerais, Belo Horizonte 30510-000, Brazil
Interests: quantum correlation; magnon bands; topological phase transition; spin and thermal Hall effect; frustrated magnetism
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Special Issue Information

Dear Colleagues,

In recent years, there has been an large interest in understanding entanglement properties in quantum spin systems, such as the XXZ model of integer and half-integer spin, the Hubbard model, Bose–Hubbard, and so on, as well as in non-equilibrium quantum spin systems. In general, for spin systems, like the quantum one-dimensional XXZ model, their properties may depend on spin value, the geometry of the lattice and different types of interactions within the system: Dzyaloshinskii–Moriya interaction, single-ion anisotropy, spin–phonon coupling, and so on. For instance, it is well known that in the quantum one-dimensional Heisenberg model (XXZ model in the isotropic point), there is a gap in the spectrum (Haldane’s gap). The same model, of half-integer spin, is gapless due to the Lieb, Schultz and Mattis theorem. Moreover, elementary excitations are different in each case (integer and half-integer spin). While in the former (integer spin), the excitations are magnons, in the second (half-integer spin), the excitations are spinons. In addition, many models may present different types of quantum and topological phase transitions, induced by the different types of couplings present in the system.

Recently, there has been an interest in understanding the interplay between quantum entanglement and quantum phase transition in quantum spin systems both in equilibrium and in non-equilibrium. The analysis of the bipartite entanglement between two partitions of the system is not well understood yet. In general, close to the critical point, there are large effects of quantum fluctuations on quantum entanglement, where, in general, the correlation length, ξ, is much larger than the lattice spacing, a, and the low-lying excitations and the long-distance behavior of the correlations in the ground state are believed to be described by a quantum field theory in 1+1 dimensions. For a 1+1-dimensional theory at the critical point, one can derive analogous expressions for reduced density matrix entropy and other measures of entanglement such as entanglement negativity, quantum discord, and so on.

Prof. Dr. Leonardo dos Santos Lima
Guest Editor

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Keywords

  • thermal and spin Hall transport
  • spin Hall effect
  • spintronics
  • longitudinal spin transport
  • quantum spin one-half and integer spin Heisenberg model
  • topological phase transition
  • quantum entanglement
  • magnon bands
  • stochastic differential equations and Fokker–Planck equations

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Published Papers (3 papers)

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24 pages, 4919 KiB  
Article
Quantum Error Mitigation in Optimized Circuits for Particle-Density Correlations in Real-Time Dynamics of the Schwinger Model
by Domenico Pomarico, Mahul Pandey, Riccardo Cioli, Federico Dell’Anna, Saverio Pascazio, Francesco V. Pepe, Paolo Facchi and Elisa Ercolessi
Entropy 2025, 27(4), 427; https://doi.org/10.3390/e27040427 - 14 Apr 2025
Viewed by 186
Abstract
Quantum computing gives direct access to the study of the real-time dynamics of quantum many-body systems. In principle, it is possible to directly calculate non-equal-time correlation functions, from which one can detect interesting phenomena, such as the presence of quantum scars or dynamical [...] Read more.
Quantum computing gives direct access to the study of the real-time dynamics of quantum many-body systems. In principle, it is possible to directly calculate non-equal-time correlation functions, from which one can detect interesting phenomena, such as the presence of quantum scars or dynamical quantum phase transitions. In practice, these calculations are strongly affected by noise, due to the complexity of the required quantum circuits. As a testbed for the evaluation of the real-time evolution of observables and correlations, the dynamics of the Zn Schwinger model in a one-dimensional lattice is considered. To control the computational cost, we adopt a quantum–classical strategy that reduces the dimensionality of the system by restricting the dynamics to the Dirac vacuum sector and optimizes the embedding into a qubit model by minimizing the number of three-qubit gates. The time evolution of particle-density operators in a non-equilibrium quench protocol is both simulated in a bare noisy condition and implemented on a physical IBM quantum device. In either case, the convergence towards a maximally mixed state is targeted by means of different error mitigation techniques. The evaluation of the particle-density correlation shows a well-performing post-processing error mitigation for properly chosen coupling regimes. Full article
(This article belongs to the Special Issue Entanglement in Quantum Spin Systems)
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18 pages, 2348 KiB  
Article
Efficiently Characterizing the Quantum Information Flow, Loss, and Recovery in the Central Spin System
by Jiahui Chen, Mohamad Niknam and David Cory
Entropy 2024, 26(12), 1077; https://doi.org/10.3390/e26121077 - 10 Dec 2024
Viewed by 932
Abstract
Understanding the flow, loss, and recovery of the information between a system and its environment is essential for advancing quantum technologies. The central spin system serves as a useful model for a single qubit, offering valuable insights into how quantum systems can be [...] Read more.
Understanding the flow, loss, and recovery of the information between a system and its environment is essential for advancing quantum technologies. The central spin system serves as a useful model for a single qubit, offering valuable insights into how quantum systems can be manipulated and protected from decoherence. This work uses the stimulated echo experiment to track the information flow between the central spin and its environment, providing a direct measure of the sensitivity of system/environment correlations to environmental dynamics. The extent of mixing and the growth of correlations are quantified through autocorrelation functions of the noise and environmental dynamics, which also enable the estimation of nested commutators between the system/environment and environmental Hamiltonians. Complementary decoupling experiments offer a straightforward measure of the strength of the system Hamiltonians. The approach is experimentally demonstrated on a spin system. Full article
(This article belongs to the Special Issue Entanglement in Quantum Spin Systems)
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11 pages, 1800 KiB  
Article
Interplay of Spin Nernst Effect and Entanglement Negativity in Layered Ferrimagnets: A Study via Exact Diagonalization
by Leonardo S. Lima
Entropy 2024, 26(12), 1060; https://doi.org/10.3390/e26121060 - 6 Dec 2024
Viewed by 684
Abstract
In this paper, we analyzed the influence of the spin Nernst effect on quantum correlation in a layered ferrimagnetic model. In the study of three-dimensional ferrimagnets, the focus is on materials with a specific arrangement of spins, where the neighboring spins are parallel [...] Read more.
In this paper, we analyzed the influence of the spin Nernst effect on quantum correlation in a layered ferrimagnetic model. In the study of three-dimensional ferrimagnets, the focus is on materials with a specific arrangement of spins, where the neighboring spins are parallel and the others are antiparallel. The anisotropic nature of these materials means that the interactions between spins depend on their relative orientations in different directions. We analyzed the effect of magnon bands induced by the coupling parameters on entanglement negativity. The influence of the coupling parameters of the topologic phase transition on quantum entanglement is investigated as well. Numerical simulations using the Lanczos algorithm and exact diagonalization for different lattice sizes are compared with the results of spin wave theory. Full article
(This article belongs to the Special Issue Entanglement in Quantum Spin Systems)
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