ENTANGLEMENT DEGRADATION IN A STRING OF ATOMS COUPLED BY THE ELECTROMAGNETIC FIELD

2004 ◽  
Vol 04 (03) ◽  
pp. L511-L519 ◽  
Author(s):  
PÉTER FÖLDI ◽  
MIHÁLY G. BENEDICT ◽  
TAMÁS SERÉNYI ◽  
ATTILA CZIRJÁK
Keyword(s):  
Electromagnetic Field ◽  
Time Evolution ◽  
Dipole Interaction ◽  
Environmental Noise ◽  
Multipartite Entanglement ◽  
Initial State ◽  
Linear Chains ◽  
Initial Stage ◽  
Entanglement Witnesses ◽  
Two Level Systems

We investigate the dynamics of short linear chains consisting of two-level systems (atoms) coupled by the electromagnetic field. The environment of photon modes acts as a source of noise and leads to the disappearance of the initially present multipartite entanglement. The rate of this process (entanglement degradation) depends on the separation of the atoms, and also on the initial state. With the aid of the appropriate entanglement witnesses we show that this rate is exceptionally low for the so-called subradiant states. Below one resonant wavelength of atomic separation the effect of the environmental noise is weaker than the dipole-dipole interaction and multipartite entanglement can be formed in the initial stage of the time evolution.

Density matrix and purity evolution in dissipative two-level systems: II. Relaxation

2021 ◽  
Author(s):  
Sambarta Chatterjee ◽  
Nancy Makri
Keyword(s):  
Density Matrix ◽  
Time Evolution ◽  
Reduced Density Matrix ◽  
Level System ◽  
Two Level Systems ◽  
Reduced Density ◽  
Harmonic Bath

We investigate the time evolution of the reduced density matrix (RDM) and its purity in the dynamics of a two-level system coupled to a dissipative harmonic bath, when the system is initially placed in one of its eigenstates.

scholarly journals Using Matrix-Product States for Open Quantum Many-Body Systems: Efficient Algorithms for Markovian and Non-Markovian Time-Evolution

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 984
Author(s):  
Regina Finsterhölzl ◽  
Manuel Katzer ◽  
Andreas Knorr ◽  
Alexander Carmele
Keyword(s):  
Time Evolution ◽  
Nearest Neighbor ◽  
Matrix Product ◽  
Body System ◽  
Many Body ◽  
Initial State ◽  
Matrix Product States ◽  
Open Quantum ◽  
Many Body Systems ◽  
The Many

This paper presents an efficient algorithm for the time evolution of open quantum many-body systems using matrix-product states (MPS) proposing a convenient structure of the MPS-architecture, which exploits the initial state of system and reservoir. By doing so, numerically expensive re-ordering protocols are circumvented. It is applicable to systems with a Markovian type of interaction, where only the present state of the reservoir needs to be taken into account. Its adaption to a non-Markovian type of interaction between the many-body system and the reservoir is demonstrated, where the information backflow from the reservoir needs to be included in the computation. Also, the derivation of the basis in the quantum stochastic Schrödinger picture is shown. As a paradigmatic model, the Heisenberg spin chain with nearest-neighbor interaction is used. It is demonstrated that the algorithm allows for the access of large systems sizes. As an example for a non-Markovian type of interaction, the generation of highly unusual steady states in the many-body system with coherent feedback control is demonstrated for a chain length of N=30.

INFLUENCE OF INTRINSIC DECOHERENCE ON THE ENTANGLEMENT BETWEEN TWO ATOMS IN TAVIS–CUMMINGS MODEL

2008 ◽  
Vol 06 (01) ◽  
pp. 167-179
Author(s):  
CHUAN-JIA SHAN ◽  
WEI-WEN CHENG ◽  
TANG-KUN LIU ◽  
YAN-XIA HUANG ◽  
HONG LI ◽  
...  
Keyword(s):  
Strong Coupling ◽  
Quantum State ◽  
Dipole Interaction ◽  
Entangled State ◽  
Entanglement Dynamics ◽  
Initial State ◽  
Intrinsic Decoherence ◽  
Dipole Coupling ◽  
Fock State

Considering the dipole–dipole coupling intensity between two atoms and the field in the Fock state, the entanglement dynamics between two atoms that are initially entangled in the Tavis–Cummings model with intrinsic decoherence have been investigated. The two-atom entanglement appears with periodicity without considering intrinsic decoherence. However, the intrinsic decoherence causes the decay of entanglement between two atoms, with the decrease of the intrinsic decoherence coefficient, the entanglement will quickly become a constant value, which is affected by the two-atom initial state, the dipole–dipole coupling intensity and the field in the Fock state. Meanwhile, the two-atom quantum state will stay forever in the maximal entangled state when the initial state is proper, even in the presence of intrinsic decoherence. Furthermore, the two atoms can generate maximal entangled state even if they are initially separated by adjusting the dipole–dipole interaction, the strong coupling can improve the value of entanglement.

scholarly journals KUBAN UKRAINIZATION INITIAL STATE IN THE KUBAN EMERGENCY PARLIAMENT MEETING MATERIALS

2018 ◽  
pp. 109-113
Author(s):  
A. V. Markin
Keyword(s):  
Initial State ◽  
Language And Culture ◽  
Initial Stage ◽  
National Movements

The article is devoted to the initial stage of Ukrainization in the Kuban, which consisted mainly of a purposeful and consistent introduction of the Ukrainian language and culture into the life of the population. After the February 1917 events in Russia, various national movements, where they were present, sharply intensified. In particular, the Cuban-Ukrainian movement in the Kuban also became more active. Initially, measures for this implementation were planned to be implemented in the sphere of education, mainly school. At the first stage it was spontaneous, at the initiative of the inhabitants of some localities, but with the support of the Kuban Territorial and legislative rads. The Kuban Parliament, immediately after its formation in March 1917, announced to the Provisional Government its plans to create an extensive network of Ukrainian schools, to use the Ukrainian language more widely, to promote its implementation in church services.

scholarly journals Quantum-Heat Fluctuation Relations in Three-Level Systems Under Projective Measurements

2020 ◽  
Vol 5 (1) ◽  
pp. 17 ◽  
Author(s):  
Guido Giachetti ◽  
Stefano Gherardini ◽  
Andrea Trombettoni ◽  
Stefano Ruffo
Keyword(s):  
Energy Scale ◽  
Quantum Measurements ◽  
Thermal Component ◽  
Initial State ◽  
Fluctuation Relations ◽  
N Level ◽  
Two Level Systems ◽  
Jarzynski Equality ◽  
Projective Measurements

We study the statistics of energy fluctuations in a three-level quantum system subject to a sequence of projective quantum measurements. We check that, as expected, the quantum Jarzynski equality holds provided that the initial state is thermal. The latter condition is trivially satisfied for two-level systems, while this is generally no longer true for N-level systems, with N > 2 . Focusing on three-level systems, we discuss the occurrence of a unique energy scale factor β eff that formally plays the role of an effective inverse temperature in the Jarzynski equality. To this aim, we introduce a suitable parametrization of the initial state in terms of a thermal and a non-thermal component. We determine the value of β eff for a large number of measurements and study its dependence on the initial state. Our predictions could be checked experimentally in quantum optics.

The influence of nonlinear bottom friction on the properties of decaying cyclonic and anticyclonic vortex structures in a shallow rotated fluid

2014 ◽  
Vol 753 ◽  
pp. 217-241 ◽  
Author(s):  
S. V. Kostrykin ◽  
A. A. Khapaev ◽  
I. G. Yakushkin
Keyword(s):  
Horizontal Plane ◽  
Laboratory Experiments ◽  
Initial State ◽  
Turbulent Eddy ◽  
Modified Model ◽  
Initial Stage ◽  
Free Decay ◽  
Axisymmetric Vortex ◽  
Theoretical Predictions ◽  
Eddy Flow

AbstractThe problem of the decay of intense vortices in a shallow rotated neutrally stratified fluid is considered using simulations with a modified model of von Kármán type and laboratory experiments. The numerical model describes a forced axisymmetric vortex, vertically confined, but infinite in the horizontal plane. It may be used for comparisons with laboratory experiments, in which a quasi-turbulent eddy flow is generated, using magnetohydrodynamic forcing. A detailed analysis of simulations of the free decay of the flow from an initial state, given either by an arbitrary Poiseuille or by a forced stationary profile of vorticity, is provided. Based on this analysis, three different regimes of decay of intense anticyclones in the parameter space of the Ekman and initial Rossby numbers are found. It is shown that anticyclones with large enough Rossby and small enough Ekman numbers may decay to a non-trivial stationary state, or at least they decay much slower than cyclones of the same intensity. The laboratory experiments show much slower decay of intense anticyclones than weak anticyclones or cyclones, and also a dominance of anticyclones over cyclones during the initial stage of decay. These observations qualitatively agree with theoretical predictions.

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