Scaling of entanglement at quantum phase transition for two-dimensional array of quantum dots

With Hubbard model, the entanglement scaling behavior in a two-dimensional itinerant system is investigated. It has been found that, on the two sides of the critical point denoting an inherent quantum phase transition (QPT), the entanglement follows different scalings with the size just as an order parameter does. This fact reveals the subtle role played by the entanglement in QPT as a fungible physical resource

Entanglement Switch for Dipole Arrays

We propose a new entanglement switch of qubits consisting of electric dipoles, oriented along or against an external electric field and coupled by the electric dipole-dipole interaction. The pairwise entanglement can be tuned and controlled by the ratio of the Rabi frequency and the dipole-dipole coupling strength. Tuning the entanglement can be achieved for one, two and three-dimensional arrangements of the qubits. The feasibility of building such an entanglement switch is also discussed.Comment: 6 pages and 4 figures. To be published on Journal of Chemical Physic

Synthesis and Characterization of Some Novel Oxazine, Thiazine and Pyrazol Derivatives

In this paper, some chalcone derivatives (C1, C2) were synthesized based on the reaction of equal amount of substituted acetophenone and substituted banzaldehyde in basic medium. Oxazine and thiazine derivatives were prepared from the reaction of chalcones (C1-C2) with urea and thiourea respectively in a basic medium. Pyrazole derivatives were prepared based on the reaction of chalcones with hydrazine mono hydrate or phenyl hydrazine in the presence of glacial acetic acid as a catalyst. The new synthesized compounds were identified using various physical techniques like1 H-NMR and FT-IR spectra

Simulated Quantum Computation of Global Minima

Finding the optimal solution to a complex optimization problem is of great importance in practically all fields of science, technology, technical design and econometrics. We demonstrate that a modified Grover's quantum algorithm can be applied to real problems of finding a global minimum using modest numbers of quantum bits. Calculations of the global minimum of simple test functions and Lennard-Jones clusters have been carried out on a quantum computer simulator using a modified Grover's algorithm. The number of function evaluations $N$ reduced from O(N) in classical simulation to $O(\sqrt{N})$ in quantum simulation. We also show how the Grover's quantum algorithm can be combined with the classical Pivot method for global optimization to treat larger systems.Comment: 6 figures. Molecular Physics, in pres

Universal Programmable Quantum Circuit Schemes to Emulate an Operator

Unlike fixed designs, programmable circuit designs support an infinite number of operators. The functionality of a programmable circuit can be altered by simply changing the angle values of the rotation gates in the circuit. Here, we present a new quantum circuit design technique resulting in two general programmable circuit schemes. The circuit schemes can be used to simulate any given operator by setting the angle values in the circuit. This provides a fixed circuit design whose angles are determined from the elements of the given matrix-which can be non-unitary-in an efficient way. We also give both the classical and quantum complexity analysis for these circuits and show that the circuits require a few classical computations. They have almost the same quantum complexities as non-general circuits. Since the presented circuit designs are independent from the matrix decomposition techniques and the global optimization processes used to find quantum circuits for a given operator, high accuracy simulations can be done for the unitary propagators of molecular Hamiltonians on quantum computers. As an example, we show how to build the circuit design for the hydrogen molecule.Comment: combined with former arXiv:1207.174

Dynamics of entanglement in a two-dimensional spin system

We consider the time evolution of entanglement in a finite two dimensional transverse Ising model. The model consists of a set of 7 localized spin-1/2 particles in a two dimensional triangular lattice coupled through nearest neighbor exchange interaction in presence of an external time dependent magnetic field. The magnetic field is applied in different function forms: step, exponential, hyperbolic and periodic. We found that the time evolution of the entanglement shows an ergodic behavior under the effect of the time dependent magnetic fields. Also we found that while the step magnetic field causes great disturbance to the system creating rabid oscillations, the system shows great controllability under the effect of the other magnetic fields where the entanglement profile follows closely the shape of the applied field even with the same frequency for periodic fields. This follow up trend breaks down as the strength of the field, the transition constant for exponential and hyperbolic, or frequency for periodic field increase leading to rapid oscillations. We observed that the entanglement is very sensitive to the initial value of the applied periodic field, the smaller the initial value the less distorted is the entanglement profile. Furthermore, the effect of thermal fluctuations is very devastating to the entanglement which decays very rapidly as the temperature increases. Interestingly, although large value of the magnetic field strength may yield small entanglement, it was found to be more persistent against thermal fluctuations than the small field strengths

The optimal choice of the spectra bandwidth for a random field

In this paper, we give a criterion to choice the spectral bandwidth in the smoothing periodogram via spectral windows to estimate the spectral density for a stationary random field . As for the estimation of the probability density, the cross validation method proposed here is based on the integrated square error estimation using the principle of "leave-out-I" .Ce travail présente une procédure pour choisir la largeur de la fenêtre spectrale utilisée dans le lissage d'un périodogramme lors de l'estimation de la densité spectrale d'un champ aléatoire stationnaire. La procédure de validation croisée que nous proposons est basée, comme pour l'estimation de la densité de probabilité, sur l'estimation de l'erreur quadratique intégrée (ISE) en utilisant le principe du « Leave-out-I »

Decomposition of Unitary Matrices for Finding Quantum Circuits: Application to Molecular Hamiltonians

Constructing appropriate unitary matrix operators for new quantum algorithms and finding the minimum cost gate sequences for the implementation of these unitary operators is of fundamental importance in the field of quantum information and quantum computation. Evolution of quantum circuits faces two major challenges: complex and huge search space and the high costs of simulating quantum circuits on classical computers. Here, we use the group leaders optimization algorithm to decompose a given unitary matrix into a proper-minimum cost quantum gate sequence. We test the method on the known decompositions of Toffoli gate, the amplification step of the Grover search algorithm, the quantum Fourier transform, and the sender part of the quantum teleportation. Using this procedure, we present the circuit designs for the simulation of the unitary propagators of the Hamiltonians for the hydrogen and the water molecules. The approach is general and can be applied to generate the sequence of quantum gates for larger molecular systems

Effets du calibre et de la durée du stockage des semences sur la germination des graines d’Anthyllis cytisoides L. dans l'Oriental du Maroc

Spontaneous shrub A. cytisoides L. is a leguminous species of fodder used for livestock feed, due to its high digestibility and its high protein content. The objective of this study, which is a continuation of a study started in 2016, is to test the hypothesis that morphological dormancy and seed storage duration have an impact on the germination rate of A. cytisoides. To achieve this goal, we have investigated two types of seeds: small and large seeds. In addition, we used three lots of seeds, during our trials: 2008, 2009 and 2010. Results show that morphological dormancy has a highly significant effect on the germination rates of A. cytisoides, especially on the large seeds (96%), and 28% for the small seeds. However, the storage has no significant effect on the emergence rate of seeds.Anthyllis cytisoides est un arbuste légumineux spontané apprécié par le bétail, digestible et riche en protéines. Ce travail, qui est une continuité d'une étude entamée depuis 2016, appréhende les effets du calibre et de la durée du stockage des semences sur leur germination. Deux formes de graines sont examinées pour le calibre (petites et grosses); et trois lots de graines pour des durées de stockage d’une, de deux et de trois années (2008, 2009 et 2010). Les résultats obtenus montrent un effet très significatif du calibre des graines sur le taux de germination: 96% chez les grosses graines, versus 28% chez les petites seulement. Par contre, in n'y a pas de différence significative de l'effet de la durée du stockage sur la germination. Les trois durées de conservation des semences semblent avoir le même comportement morphologique : 60; 60,5 et 66% respectivement pour les semences de 2010, 2008 et 2009.Cesrésultats aideraient à améliorer la régénération et la restauration d’A. cytisoides dans l'Oriental