Quantum Information and Symmetry

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Physics".

Deadline for manuscript submissions: closed (15 January 2020) | Viewed by 19152

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Faculty of Physics and Astronomy, Univeristy of Zielona Góra, ul. Z. Szafrana 4a, 65-516 Zielona Góra, Poland
Interests: quantum and nonlinear optics; quantum information theory; deterministic chaos; quantum chaos; cellular automata
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Guest Editor
Faculty of Physics and Astronomy, Univeristy of Zielona Góra, Prof. Z. Szafrana 4a, 65-516 Zielona Góra, Poland
Interests: quantum optics; quantum information theory; quantum chaos; deterministic chaos

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Institute of Physics, Częstochowa University of Technology, Armii Krajowej 19, 42-200 Częstochowa, Poland
Interests: solid state physics; superconducting; quantum information theory; chaos theory

Special Issue Information

 Dear Colleagues,

Recent research in the fields related to the quantum information theory (QIT) became one of the most intriguing and promising investigations in contemporary physics. Many novel QIT concepts are discussed in the literature, and the broad range of new models of quantum optics and solid state physics are recently considered in the context of QIT. For instance, new ideas concerning optical lattices, superconducting devices, nano-resonators, circuit QED models, nonlinear Kerr-like systems were topics of the numerous papers. Such articles were devoted not only to various aspects of quantum correlations such as quantum entanglement, quantum steering, EPR correlations or quantum discord but also to more practical proposals of the systems which could be applied in the quantum teleportation, quantum coding, quantum computing, etc. On the other hand, the ideas of symmetry are widely discussed in all physical sciences. They have become keystones of various concepts and considerations leading to the novel discoveries in physics. Thus, this Special issue is devoted to the broad range of QIT topics which are related to the ideas of symmetry. We would like to invite all Colleagues to submit their original research, review and short communication articles to the issue. Both theoretical and experimental submissions are welcome.

Prof. Wiesław Leonski
Dr. Joanna K. Kalaga
Prof. Radosław Szczęśniak
Guest Editors

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Keywords

  • quantum optics
  • solid state physics
  • symmetry of quantum states
  • PT-symmetric Hamiltonians
  • nano-cavities
  • circuit QED
  • Copper pairs systems
  • quantum state engineering
  • EPR correlations
  • quantum entanglement
  • discord and steering

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Published Papers (7 papers)

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Research

10 pages, 392 KiB  
Article
Solitonic Fixed Point Attractors in the Complex Ginzburg–Landau Equation for Associative Memories
by Alexey N. Pyrkov, Tim Byrnes and Valentin V. Cherny
Symmetry 2020, 12(1), 24; https://doi.org/10.3390/sym12010024 - 20 Dec 2019
Cited by 2 | Viewed by 2503
Abstract
It was recently shown that the nonlinear Schrodinger equation with a simplified dissipative perturbation features a zero-velocity solitonic solution of non-zero amplitude which can be used in analogy to attractors of Hopfield’s associative memory. In this work, we consider a more complex dissipative [...] Read more.
It was recently shown that the nonlinear Schrodinger equation with a simplified dissipative perturbation features a zero-velocity solitonic solution of non-zero amplitude which can be used in analogy to attractors of Hopfield’s associative memory. In this work, we consider a more complex dissipative perturbation adding the effect of two-photon absorption and the quintic gain/loss effects that yields the complex Ginzburg–Landau equation (CGLE). We construct a perturbation theory for the CGLE with a small dissipative perturbation, define the behavior of the solitonic solutions with parameters of the system and compare the solution with numerical simulations of the CGLE. We show, in a similar way to the nonlinear Schrodinger equation with a simplified dissipation term, a zero-velocity solitonic solution of non-zero amplitude appears as an attractor for the CGLE. In this case, the amplitude and velocity of the solitonic fixed point attractor does not depend on the quintic gain/loss effects. Furthermore, the effect of two-photon absorption leads to an increase in the strength of the solitonic fixed point attractor. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
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22 pages, 337 KiB  
Article
The Symmetry of Pairing and the Electromagnetic Properties of a Superconductor with a Four-Fermion Attraction at Zero Temperature
by Przemyslaw Tarasewicz
Symmetry 2019, 11(11), 1358; https://doi.org/10.3390/sym11111358 - 2 Nov 2019
Cited by 2 | Viewed by 1719
Abstract
Properties of a fermion system at zero temperature are investigated. The physical system is described by a Hamiltonian containing the BCS interaction and an attractive four-fermion interaction. The four-fermion potential is caused by attractions between Cooper pairs mediated by the phonon field. In [...] Read more.
Properties of a fermion system at zero temperature are investigated. The physical system is described by a Hamiltonian containing the BCS interaction and an attractive four-fermion interaction. The four-fermion potential is caused by attractions between Cooper pairs mediated by the phonon field. In this paper, the BCS interaction is assumed to be negligible and the four-fermion potential is the only one that acts in the system. The effect of the pairing symmetry used in the four-fermion potential on some zero-temperature properties is studied. This especially concerns the electromagnetic response of the system to an external magnetic field. It turns out that, in this instance, there are serious differences between the conventional BCS system and the one investigated in this paper. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
15 pages, 1831 KiB  
Article
Single-Qubit Driving Fields and Mathieu Functions
by Marco Enríquez, Alfonso Jaimes-Nájera and Francisco Delgado
Symmetry 2019, 11(9), 1172; https://doi.org/10.3390/sym11091172 - 16 Sep 2019
Cited by 1 | Viewed by 3015
Abstract
We report a new family of time-dependent single-qubit radiation fields for which the correspondent evolution operator can be disentangled in an exact way via the Wei–Norman formalism. Such fields are characterized in terms of the Mathieu functions. We show that the regions of [...] Read more.
We report a new family of time-dependent single-qubit radiation fields for which the correspondent evolution operator can be disentangled in an exact way via the Wei–Norman formalism. Such fields are characterized in terms of the Mathieu functions. We show that the regions of stability of the Mathieu functions determine the nature of the driving fields: For parameters in the stable region, the fields are oscillating, being able to be periodic under certain conditions. Whereas, for parameters in the instability region, the fields are pulse-like. In addition, in the stability region, this family admits solutions for evolution loops in quantum control. We obtain some prescriptions to reach such a control effect. Geometric phases in the evolution are also analyzed and discussed. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
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9 pages, 341 KiB  
Article
The Entanglement Generation in P T -Symmetric Optical Quadrimer System
by Joanna K. Kalaga
Symmetry 2019, 11(9), 1110; https://doi.org/10.3390/sym11091110 - 3 Sep 2019
Cited by 4 | Viewed by 2844
Abstract
We discuss a model consisting of four single-mode cavities with gain and loss energy in the first and last modes. The cavities are coupled to each other by linear interaction and form a chain. Such a system is described by a non-Hermitian Hamiltonian [...] Read more.
We discuss a model consisting of four single-mode cavities with gain and loss energy in the first and last modes. The cavities are coupled to each other by linear interaction and form a chain. Such a system is described by a non-Hermitian Hamiltonian which, under some conditions, becomes P T -symmetric. We identify the phase-transition point and study the possibility of generation bipartite entanglement (entanglement between all pairs of cavities) in the system. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
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10 pages, 363 KiB  
Article
Asymmetry of Quantum Correlations Decay in Nonlinear Bosonic System
by Anna Kowalewska-Kudłaszyk and Grzegorz Chimczak
Symmetry 2019, 11(8), 1023; https://doi.org/10.3390/sym11081023 - 8 Aug 2019
Cited by 4 | Viewed by 2314
Abstract
We study the problem of the influence of one-sided different noisy channels to the quantum correlations decay in a symmetric bosonic system. We concentrate on one type of these correlations—the entanglement. The system under consideration is composed of two nonlinear oscillators coupled by [...] Read more.
We study the problem of the influence of one-sided different noisy channels to the quantum correlations decay in a symmetric bosonic system. We concentrate on one type of these correlations—the entanglement. The system under consideration is composed of two nonlinear oscillators coupled by two-boson interactions and externally driven by a continuous coherent field. Our low-dimensional system can be treated as 2-qutrit one. Two different noisy channels (the amplitude and the phase-damping reservoirs) are applied to both of the system’s modes. We show that there is a noticeable difference in the quantum entanglement in 2-qubit subspaces of the whole system decrease after swapping the reservoirs between the modes of the considered symmetric system. It appears also that the degree of obtained entanglement depends crucially on the position of the appropriate type of reservoir. The origin of the observed asymmetry is also explained. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
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12 pages, 644 KiB  
Article
Quantum Behavior of a PT -Symmetric Two-Mode System with Cross-Kerr Nonlinearity
by Jan Peřina, Jr. and Antonín Lukš
Symmetry 2019, 11(8), 1020; https://doi.org/10.3390/sym11081020 - 7 Aug 2019
Cited by 7 | Viewed by 2912
Abstract
Quantum behavior of two oscillator modes, with mutually balanced gain and loss and coupled via linear coupling (including energy conserving as well as energy non-conserving terms) and nonlinear cross-Kerr effect, is investigated. Stationary states are found and their stability analysis is given. Exceptional [...] Read more.
Quantum behavior of two oscillator modes, with mutually balanced gain and loss and coupled via linear coupling (including energy conserving as well as energy non-conserving terms) and nonlinear cross-Kerr effect, is investigated. Stationary states are found and their stability analysis is given. Exceptional points for PT -symmetric cases are identified. Quantum dynamics treated by the model of linear operator corrections to a classical solution reveals nonclassical properties of individual modes (squeezing) as well as their entanglement. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
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12 pages, 523 KiB  
Article
Characteristics of the s–Wave Symmetry Superconducting State in the BaGe3 Compound
by Kamila A. Szewczyk, Ewa A. Drzazga-Szczȩśniak, Marcin W. Jarosik, Klaudia M. Szczȩśniak and Sandra M. Binek
Symmetry 2019, 11(8), 977; https://doi.org/10.3390/sym11080977 - 1 Aug 2019
Viewed by 2810
Abstract
Thermodynamic properties of the s–wave symmetry superconducting phase in three selected structures of the BaGe 3 compound ( P 6 3 / m m c , A m m 2 , and I 4 / m m m ) were discussed in [...] Read more.
Thermodynamic properties of the s–wave symmetry superconducting phase in three selected structures of the BaGe 3 compound ( P 6 3 / m m c , A m m 2 , and I 4 / m m m ) were discussed in the context of DFT results obtained for the Eliashberg function. This compound may enable the implementation of systems for quantum information processing. Calculations were carried out within the Eliashberg formalism due to the fact that the electron–phonon coupling constant falls within the range λ 0.73 , 0.86 . The value of the Coulomb pseudopotential was assumed to be 0.122 , in accordance with the experimental results. The value of the Coulomb pseudopotential was assumed to be 0.122 , in accordance with the experimental results. The existence of the superconducting state of three different critical temperature values, namely, 4.0 K, 4.5 K and 5.5 K, depending on the considered structure, was stated. We determined the differences in free energy ( Δ F ) and specific heat ( Δ C ) between the normal and the superconducting states, as well as the thermodynamic critical field ( H c ) as a function of temperature. A drop in the H c value to zero at the temperature of 4.0 K was observed for the P 6 3 / m m c structure, which is in good accordance with the experimental data. Further, the values of the dimensionless thermodynamic parameters of the superconducting state were estimated as: R Δ = 2 Δ ( 0 ) / k B T c { 3.68 , 3.8 , 3.8 } , R C = Δ C ( T c ) / C N ( T c ) { 1.55 , 1.71 , 1.75 } , and R H = T c C N ( T c ) / H c 2 ( 0 ) { 0.168 , 0.16 , 0.158 } , which are slightly different from the predictions of the Bardeen–Cooper–Schrieffer theory ( [ R Δ ] B C S = 3.53 , [ R C ] B C S = 1.43 , and [ R H ] B C S = 0.168 ). This is caused by the occurrence of small retardation and strong coupling effects. Full article
(This article belongs to the Special Issue Quantum Information and Symmetry)
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