scholarly journals Return probability after a quench from a domain wall initial state in the spin-1/2 XXZ chain

2017 ◽  
Vol 2017 (10) ◽  
pp. 103108 ◽  
Author(s):  
Jean-Marie Stéphan
Keyword(s):  
Domain Wall ◽  
Initial State ◽  
Return Probability ◽  
Xxz Chain

scholarly journals A limit law of the return probability for a quantum walk on a hexagonal lattice

2015 ◽  
Vol 13 (07) ◽  
pp. 1550054 ◽  
Author(s):  
Takuya Machida
Keyword(s):  
Random Walks ◽  
Discrete Time ◽  
Hexagonal Lattice ◽  
Quantum Walk ◽  
Quantum Walks ◽  
The Other ◽  
View Point ◽  
Initial State ◽  
Random Walker ◽  
Return Probability

A return probability of random walks is one of the interesting subjects. As it is well known, the return probability strongly depends on the structure of the space where the random walker moves. On the other hand, the return probability of quantum walks, which are quantum models corresponding to random walks, has also been investigated to some extend lately. In this paper, we take care of a discrete-time three-state quantum walk on a hexagonal lattice from the view point of mathematics. The mathematical result shows a limit of the return probability when the walker starts off at the origin. The result of the limit tells us about a possibility of localization at the position and a dependence of localization on the initial state.

THE EFFECT OF DIFFERENT DZYALOSHINSKII–MORIYA INTERACTIONS ON TELEPORTATION VIA A TWO-QUBIT HEISENBERG CHAIN

2010 ◽  
Vol 24 (04n05) ◽  
pp. 461-473
Author(s):  
TAO CHEN ◽  
CHUAN-JIA SHAN ◽  
YAN-XIA HUANG ◽  
TANG-KUN LIU ◽  
JIN-XING LI
Keyword(s):  
Coupling Coefficient ◽  
Coupling Parameter ◽  
Exchange Constant ◽  
Thermal Entanglement ◽  
Initial State ◽  
Dm Interaction ◽  
Maximum Value ◽  
Entanglement Teleportation ◽  
Xxz Chain ◽  
Heisenberg Chains

Thermal entanglement of a two-qubit Heisenberg XXZ chain in the presence of different Dzyaloshinskii–Moriya (DM) anisotropic antisymmetric interactions and entanglement teleportation using two independent Heisenberg chains as quantum channel are investigated. It is found that the anisotropic coupling coefficient Jz (z-component exchange constant) and DM interactions can excite the entanglement, and x-component DM interaction Dx has a more remarkable influence than the z-axis DM interaction Dz for exchange constant J > 0 (antiferromagnetic) case, which is contrary to coupling coefficient J < 0 (ferromagnetic) case. The output entanglement and fidelity increase with increasing z-axis coupling parameter Jz for both the antiferromagnetic J > 0 case and ferromagnetic J < 0 case. By introducing the different DM interactions, it is superior to teleportate initial state by using the Dz interaction in the model for J > 0 case. But for J < 0 case, the Dx interaction is better, and the output concurrence and fidelity can reach the maximum value 1 with suitable Dx.

scholarly journals How to probe the microscopic onset of irreversibility with ultracold atoms

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
R. Bürkle ◽  
A. Vardi ◽  
D. Cohen ◽  
J. R. Anglin
Keyword(s):  
Phase Space ◽  
Ultracold Atoms ◽  
Open Systems ◽  
Cold Atom ◽  
Experimental Demonstration ◽  
Dynamical Chaos ◽  
Initial State ◽  
Return Probability ◽  
Isolated Systems ◽  
Fundamental Mechanism

Abstract The microscopic onset of irreversibility is finally becoming an experimental subject. Recent experiments on microscopic open and even isolated systems have measured statistical properties associated with entropy production, and hysteresis-like phenomena have been seen in cold atom systems with dissipation (i.e. effectively open systems coupled to macroscopic reservoirs). Here we show how experiments on isolated systems of ultracold atoms can show dramatic irreversibility like cooking an egg. In our proposed experiments, a slow forward-and-back parameter sweep will sometimes fail to return the system close to its initial state. This probabilistic hysteresis is due to the same non-adiabatic spreading and ergodic mixing in phase space that explains macroscopic irreversibility, but realized without dynamical chaos; moreover this fundamental mechanism quantitatively determines the probability of return to the initial state as a function of tunable parameters in the proposed experiments. Matching the predicted curve of return probability will be a conclusive experimental demonstration of the microscopic onset of irreversibility.

scholarly journals Domain wall problem in the quantum XXZ chain and semiclassical behavior close to the isotropic point

2019 ◽  
Vol 7 (2) ◽  
Author(s):  
Grégoire Misguich ◽  
Nicolas Pavloff ◽  
Vincent Pasquier
Keyword(s):  
Domain Wall ◽  
Entanglement Entropy ◽  
Spin Correlation ◽  
Quantitative Agreement ◽  
Isotropic Point ◽  
Density Matrix Renormalization ◽  
Energy Current ◽  
Quantum Chain ◽  
Xxz Chain ◽  
Long Time

We study the dynamics of a spin-\frac{1}{2}12 XXZ chain which is initially prepared in a domain-wall state. We compare the results of time-dependent Density Matrix Renormalization Group simulations with those of an effective description in terms of a classical anisotropic Landau-Lifshitz (LL) equation. Numerous quantities are analyzed: magnetization (xx, yy and zz components), energy density, energy current, but also some spin-spin correlation functions or entanglement entropy in the quantum chain. Without any adjustable parameter a quantitative agreement is observed between the quantum and the LL problems in the long time limit, when the models are close to the isotropic point. This is explained as a consequence of energy conservation. At the isotropic point the mapping between the LL equation and the nonlinear Schrödinger equation is used to construct a variational solution capturing several aspects of the problem.

scholarly journals Universal front propagation in the quantum Ising chain with domain-wall initial states

2016 ◽  
Vol 1 (2) ◽  
Author(s):  
Viktor Eisler ◽  
Florian Maislinger ◽  
Hans Gerd Evertz
Keyword(s):  
Domain Wall ◽  
Domain Walls ◽  
Entanglement Entropy ◽  
Front Propagation ◽  
Ferromagnetic Phase ◽  
Xy Model ◽  
Zero Field ◽  
Ising Chain ◽  
Initial State ◽  
Longitudinal Magnetization

We study the melting of domain walls in the ferromagnetic phase of the transverse Ising chain, created by flipping the order-parameter spins along one-half of the chain. If the initial state is excited by a local operator in terms of Jordan-Wigner fermions, the resulting longitudinal magnetization profiles have a universal character. Namely, after proper rescalings, the profiles in the noncritical Ising chain become identical to those obtained for a critical free-fermion chain starting from a step-like initial state. The relation holds exactly in the entire ferromagnetic phase of the Ising chain and can even be extended to the zero-field XY model by a duality argument. In contrast, for domain-wall excitations that are highly non-local in the fermionic variables, the universality of the magnetization profiles is lost. Nevertheless, for both cases we observe that the entanglement entropy asymptotically saturates at the ground-state value, suggesting a simple form of the steady state.

scholarly journals Entanglement spreading after local fermionic excitations in the XXZ chain

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Matthias Gruber ◽  
Viktor Eisler
Keyword(s):  
Spectral Weight ◽  
Majorana Fermion ◽  
Density Matrix Renormalization Group ◽  
Initial State ◽  
Conformal Field ◽  
Multiplicative Factor ◽  
Density Matrix Renormalization ◽  
Liquid Theory ◽  
Xxz Chain ◽  
Theory Framework

We study the spreading of entanglement produced by the time evolution of a local fermionic excitation created above the ground state of the XXZ chain. The resulting entropy profiles are investigated via density-matrix renormalization group calculations, and compared to a quasiparticle ansatz. In particular, we assume that the entanglement is dominantly carried by spinon excitations traveling at different velocities, and the entropy profile is reproduced by a probabilistic expression involving the density fraction of the spinons reaching the subsystem. The ansatz works well in the gapless phase for moderate values of the XXZ anisotropy, eventually deteriorating as other types of quasiparticle excitations gain spectral weight. Furthermore, if the initial state is excited by a local Majorana fermion, we observe a nontrivial rescaling of the entropy profiles. This effect is further investigated in a conformal field theory framework, carrying out calculations for the Luttinger liquid theory. Finally, we also consider excitations creating an antiferromagnetic domain wall in the gapped phase of the chain, and find again a modified quasiparticle ansatz with a multiplicative factor.

Electron Microscopy of Graphite Intercalation Compounds

1982 ◽  
Vol 40 ◽  
pp. 544-545
Author(s):  
G. Timp ◽  
L. Salamanca-Riba ◽  
L.W. Hobbs ◽  
G. Dresselhaus ◽  
M.S. Dresselhaus
Keyword(s):  
Electron Microscopy ◽  
Phase Transitions ◽  
Domain Wall ◽  
Intercalation Compounds ◽  
Lattice Plane ◽  
Wall Model ◽  
Graphite Intercalation Compounds ◽  
Fundamental Symmetry ◽  
Graphite Intercalation

Electron microscopy can be used to study structures and phase transitions occurring in graphite intercalations compounds. The fundamental symmetry in graphite intercalation compounds is the staging periodicity whereby each intercalate layer is separated by n graphite layers, n denoting the stage index. The currently accepted model for intercalation proposed by Herold and Daumas assumes that the sample contains equal amounts of intercalant between any two graphite layers and staged regions are confined to domains. Specifically, in a stage 2 compound, the Herold-Daumas domain wall model predicts a pleated lattice plane structure.

The direct determination of magnetic domain wall profiles using a split detector STEM

1978 ◽  
Vol 36 (1) ◽  
pp. 466-467
Author(s):  
J.N. Chapman ◽  
P.E. Batson ◽  
E.M. Waddell ◽  
R.P. Ferrier
Keyword(s):  
Electron Microscope ◽  
Domain Wall ◽  
Transmission Electron Microscope ◽  
Domain Walls ◽  
Photographic Plate ◽  
Magnetic Domain ◽  
Direct Determination ◽  
Quantitative Information ◽  
Scanning Transmission Electron Microscope ◽  
Transmission Electron

By far the most commonly used mode of Lorentz microscopy in the examination of ferromagnetic thin films is the Fresnel or defocus mode. Use of this mode in the conventional transmission electron microscope (CTEM) is straightforward and immediately reveals the existence of all domain walls present. However, if such quantitative information as the domain wall profile is required, the technique suffers from several disadvantages. These include the inability to directly observe fine image detail on the viewing screen because of the stringent illumination coherence requirements, the difficulty of accurately translating part of a photographic plate into quantitative electron intensity data, and, perhaps most severe, the difficulty of interpreting this data. One solution to the first-named problem is to use a CTEM equipped with a field emission gun (FEG) (Inoue, Harada and Yamamoto 1977) whilst a second is to use the equivalent mode of image formation in a scanning transmission electron microscope (STEM) (Chapman, Batson, Waddell, Ferrier and Craven 1977), a technique which largely overcomes the second-named problem as well.

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