scholarly journals Thermal Quantum Coherence properties in Two-Qubit Heisenberg XXX Model in Nonhomogeneous Magnetic Field

2021 ◽  
Author(s):  
Asad Ali ◽  
Muhammad Anees Khan
Keyword(s):  
Magnetic Field ◽  
Quantum Coherence ◽  
Uniform Magnetic Field ◽  
Coupling Parameter ◽  
Magnetic Interaction ◽  
Threshold Value ◽  
Quantum Correlations ◽  
Qubit System ◽  
Xxx Model ◽  
Heisenberg Xxx Model

We investigate the behavior of thermal quantum coherence in the Heisenberg XXX model for a two-qubit system placed in independently controllable Inhomogeneous magnetic fields applied to two qubits respectively. We discuss the behavior of quantum coherence by systematically varying the coupling parameter, magnetic field, and temperature for both ferromagnetic and antiferromagnetic cases. The results show the interesting behavior of quantum coherence in a certain range of parameters. Generally, it is observed that quantum correlations decay with temperature, but in the ferromagnetic case with uniform magnetic interaction, it rises with temperature up to a certain threshold value and ultimately it decreases its value to zero. Moreover, it is observed that preserving the quantum coherence for small temperatures is very hard with the increasing magnetic field because, at small temperatures, quantum coherence decays sharply with the increase in magnetic field whereas at larger temperatures it decays completely at fairly large values of the magnetic field. The variation of quantum coherence with uniform magnetic field in the antiferromagnetic case is observed to be Gaussian for larger temperature but at zero or nearly zero temperature, it behaves as a constant function for uniform magnetic field up to a threshold value and then decays to zero with an infinite slope. This shows the signature of quantum phase transition from quantum nature to classicality.

scholarly journals Revealing Trade off Relations Among Thermal Coherences and Correlations in Heisenberg XXX Model Under Inhomogeneous Magnetic Eld

2021 ◽  
Author(s):  
Asad Ali ◽  
Mustansar N Nadeem ◽  
A.H Toor ◽  
Junaid Ulhaq ◽  
Shah Ahad
Keyword(s):  
Quantum Coherence ◽  
Coupling Parameter ◽  
Quantum Fisher Information ◽  
Quantitative Relationship ◽  
Bath Temperature ◽  
Reciprocal Relationship ◽  
Entanglement Measure ◽  
Thermal Entanglement ◽  
Xxx Model ◽  
Heisenberg Xxx Model

We study the validity of quantum Fisher information (QFI) as a faithful quantum coherence and correlation quantier by drawing a comparison with subsystem's coherence measure, rst-order coherence (FOC) and the entanglement measure, Negativity to study the behavior of thermal quantum coherence and correlations in two qubit Heisenberg XXX model, placed in independently controllable magnetic eld by systematically varying the coupling parameter, magnetic eld and bath temperature for ferromagnetic and antiferromagnetic case. After carefully observing the prole of quantum coherence and correlation measures, we propose an inequality relations which shows that there may exist a quantitative relationship between QFI, Negativity and FOC in which, the equality exists at zero temperature. We identify QFI to be a more useful coherence quantier, as it quanties coherence of individual subsystems and correlations among the subsystems. On the other hand, FOC identies coherence present in the individual subsystems only. A reciprocal relationship between Negativity and FOC is also observed in dierent cases. We also observe the existence of entanglement in ferromagnetic case, in contrast to simple Heisenberg XXX model in uniform magnetic eld. We show that in the ferromagnetic case, a very small inhomogeneity in magnetic eld is capable of producing large values of thermal entanglement. This shows that the behavior of entanglement in the ferromagnetic Heisenberg system is highly unstable against inhomogeneity of magnetic elds, which is inevitably present in any solid state realization of qubits.

scholarly journals Quantum Correlated Heat Engine In XY Chainwith Dzyaloshinskii-Moriya Interactions

2021 ◽  
Author(s):  
M. Asadian ◽  
S. Ahadpour ◽  
F. Mirmasoudi
Keyword(s):  
Magnetic Field ◽  
Quantum Coherence ◽  
Heat Engine ◽  
Quantum Correlations ◽  
Orbit Interaction ◽  
Spin Orbit ◽  
Heat Engines ◽  
Surrounding Environment ◽  
Local Environments ◽  
The Magnetic Field

Abstract In this paper, we consider a heat engines composed of two interactionalqubits with spin-orbit interaction (Dzyaloshinskii–Moriya (DM)) subjectto an external magnetic field, so that each qubit is considered as a cold orhot source. One intention of this work is to investigate the following question: is it possible the effects of DM lead to improve basic thermodynamicquantities in this heat engine are coupled to local environments that arenot necessarily at equilibrium? For this end, we investigate the effects ofthe temperature and the interaction rate of each qubit with its surrounding environment on quantum correlations such as quantum coherence andquantum discord and quantum entanglements, as well as the generatedwork. Finally we compare three quantum correlations (entanglement, discord, and coherence) with thermodynamic parameters and show that theoutput work is positive for what values of the magnetic field so that thiscycle can be considered as a thermal machine.

Thermal entanglement in a mixed spin Heisenberg XXX chain with DM interaction

2021 ◽  
pp. 2150021
Author(s):  
Nizar Ahami ◽  
Morad El Baz
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Thermal Entanglement ◽  
Bipartite Entanglement ◽  
Dm Interaction ◽  
One Dimensional ◽  
Mixed Spin ◽  
Xxx Model ◽  
Moriya Interaction ◽  
Heisenberg Xxx Model

We consider a one-dimensional, mixed spin Heisenberg XXX model with an homogeneous external magnetic field and Dzyaloshinskii–Moriya interaction. Alternating spin-[Formula: see text] and spin-1 particles are forming the chain. The effect of the different parameters of the system on the bipartite thermal entanglement is studied. The type of chain used (mixed) and the size of the chain ([Formula: see text]) allow to study three types of bipartite entanglement, the qubit–qubit, qubit–qutrit and qutrit–qutrit thermal entanglement.

Thermal quantum correlations in a two-dimensional spin star model

2019 ◽  
Vol 34 (22) ◽  
pp. 1950175 ◽  
Author(s):  
Saeed Haddadi ◽  
Mohammad Reza Pourkarimi ◽  
Ahmad Akhound ◽  
Mehrdad Ghominejad
Keyword(s):  
Magnetic Field ◽  
Weak Coupling ◽  
Quantum Discord ◽  
Thermal Evolution ◽  
Coupling Parameter ◽  
Quantum Correlations ◽  
Two Dimensional ◽  
Star Model ◽  
Inhomogeneous Spin ◽  
Hamiltonian Parameters

In this paper, we study the thermal evolution of three types of quantum correlations under the homogeneous and inhomogeneous spin star Hamiltonian. It is shown that quantum discord (QD) is more stable than the other measures in the thermal regime, but concurrence is more efficient when the Hamiltonian parameters are employed. However, all quantum correlations can reach their maximum, if the inhomogeneous parameter raises. Quantum correlations can be enhanced by a weak external magnetic field and strong coupling parameter. But they vanish in the case of a strong magnetic field, weak coupling parameter, and high temperatures.

ASYMPTOTIC SOLUTION FOR THE FLOW DUE TO AN INFINITE ROTATING DISK IN THE CASE OF LARGE MAGNETIC FIELD

2000 ◽  
Vol 24 (3-4) ◽  
pp. 515-523 ◽  
Author(s):  
Tarek M.A. El-Mistakawy ◽  
Hazem A. Attia ◽  
Adel A. Megahed
Keyword(s):  
Magnetic Field ◽  
Asymptotic Expansion ◽  
Asymptotic Solution ◽  
Finite Differences ◽  
Uniform Magnetic Field ◽  
Magnetic Interaction ◽  
Rotating Disk ◽  
Exact Numerical Solution ◽  
Infinite Extent ◽  
Expansion Coefficients

The flow due to a rotating disk of infinite extent is studied in the presence of an axial uniform magnetic field in the case of large magnetic interaction number ß. The solution is given in the form of an asymptotic expansion in powers of ß-2 whose coefficients are obtained in closed form in terms of a properly scaled von Karman’s similarity coordinate that is strained to remove a secular behavior. The process of finding the expansion coefficients is found to be systematic, which makes it possible to produce as many terms of the expansion as may be needed. A comparison between the asymptotic solution and the exact numerical solution which uses finite-differences and linearization is done to check the results of the asymptotic expansion and determine its range of validity.

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