Search for: jafari--r
0.005 seconds

    Dzyaloshinskii-Moriya interaction and anisotropy effects on the entanglement of the Heisenberg model

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 79, Issue 4 , 2009 ; 10502947 (ISSN) Kargarian, M ; Jafari, R ; Langari, A ; Sharif University of Technology
    In this paper the effect of Dzyaloshinskii-Moriya interaction and anisotropy on the entanglement of Heisenberg chain has been studied. While the anisotropy suppresses the entanglement due to favoring of the alignment of spins, the DM interaction restores the spoiled entanglement via creation of the quantum fluctuations. Thermodynamic limit of the model and emerging of nonanalytic behavior of the entanglement have also been probed. The singularities of the entanglement correspond to the critical boundary separating different phases of the model. The singularity of the entanglement derivative approaches the critical point from the gapped phase and will be symmetric if both phases on the... 

    Floquet dynamical quantum phase transition in the extended XY model: Nonadiabatic to adiabatic topological transition

    , Article Physical Review B ; Volume 102, Issue 14 , 2020 Zamani, S ; Jafari, R ; Langari, A ; Sharif University of Technology
    American Physical Society  2020
    We investigate both pure and mixed states Floquet dynamical quantum phase transition (DQPT) in the periodically time-dependent extended XY model. We exactly show that the proposed Floquet Hamiltonian of interacting spins can be expressed as a sum of noninteracting quasispins imposed by an effective time dependent magnetic field (Schwinger-Rabi model). The calculated Chern number indicates that there is a topological transition from the nonadiabatic to adiabatic regime. In the adiabatic regime, the quasispins trace the time dependent effective magnetic field and then oscillate between spin up and down states. While in the nonadiabatic regime, the quasispins cannot follow the time dependent... 

    Design and construction of a fine drive system for scanning optical elements

    , Article Optics and Laser Technology ; Volume 40, Issue 6 , 2008 , Pages 803-808 ; 00303992 (ISSN) Golnabi, H ; Jafari, R ; Sharif University of Technology
    The design and operation of a simple mechanical drive system, which is able to perform a fine course of angular motion, are reported. The system consists of a lead screw, a drive nut, sine bar legs, and an output shaft that can scan the optical holder mount. With a stepper motor coupled to the lead screw and interfaced to a PC, it is possible to control the scanning operation. When a 800 step/turn motor is used, it is possible to have an angular resolution of about 0.5 mdegree for a dynamic range of about 23°. The reproducibility of the results is about 0.22% for the scan angle and the hysteresis effect of the system is in the range of 1.71%. For a total scan of 51,200 steps, a scan angle of... 

    Renormalization of entanglement in the anisotropic Heisenberg (XXZ) model

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 77, Issue 3 , 2008 ; 10502947 (ISSN) Kargarian, M ; Jafari, R ; Langari, A ; Sharif University of Technology
    We have applied our recent approach to study the quantum-information properties of the anisotropic s=1/2 Heisenberg chain. We have investigated the underlying quantum-information properties such as the evolution of concurrence, entanglement entropy, nonanalytic behaviors, and the scaling close to the quantum critical point of the model. Both the concurrence and the entanglement entropy develop two saturated values after enough iterations of the renormalization of coupling constants. These values are associated with the two different phases, i.e., Néel and spin liquid phases. The nonanalytic behavior comes from the divergence of the first derivative of both measures of entanglement as the... 

    Renormalization of concurrence: The application of the quantum renormalization group to quantum-information systems

    , Article Physical Review A - Atomic, Molecular, and Optical Physics ; Volume 76, Issue 6 , 20 December , 2007 ; 10502947 (ISSN) Kargarian, M ; Jafari, R ; Langari, A ; Sharif University of Technology
    We have combined the idea of renormalization group and quantum-information theory. We have shown how the entanglement or concurrence evolve as the size of the system becomes large, i.e., the finite size scaling is obtained. Moreover, we introduce how the renormalization-group approach can be implemented to obtain the quantum-information properties of a many-body system. We have obtained the concurrence as a measure of entanglement, its derivatives and their scaling behavior versus the size of system for the one-dimensional Ising model in transverse field. We have found that the derivative of concurrence between two blocks each containing half of the system size diverges at the critical point... 

    Design and performance of an optical fiber sensor based on light leakage

    , Article Review of Scientific Instruments ; Volume 77, Issue 6 , 2006 ; 00346748 (ISSN) Golnabi, H ; Jafari, R ; Sharif University of Technology
    Design and operation of an optical fiber sensor based on the light leakage from one fiber to another one causing intensity modulation are reported. Performance of this sensor is tested as a liquid level sensor for different liquids and the experimental results are reported. The dry and wet signals for this probe are measured for a series of measurements and important factors concerning sensor operation are described. The precision of measured values, reproducibility of the results (1.3%), and the stability of sensing operation as a function of time at different launching powers are also reported (0.8%). The reported results are promising and verify the successful operation of such a device... 

    family language policy in the city of zanjan: a city for the forlorn azerbaijani

    , Article International Journal of Multilingualism ; Volume 18, Issue 1 , 2021 , Pages 1-23 ; 14790718 (ISSN) Mirvahedi, S. H ; Jafari, R ; Sharif University of Technology
    Routledge  2021
    The study explores language maintenance and shift patterns from a family language policy perspective in Azerbaijani-Farsi bilingual families in the City of Zanjan, Iran. The city is the capital of Zanjan province which is surrounded by Azerbaijani, Kurdish, and Farsi speaking provinces giving it a specific demographic make-up to explore language maintenance and shift processes from a family language policy perspective. Thirteen parents (six fathers and seven mothers) from upper, middle, and lower socioeconomic statuses were interviewed about their language ideologies, practices, and management with respect to the maintenance of their ethnic language, Azerbaijani, and the official language of... 

    Dynamical topological quantum phase transitions at criticality

    , Article Physical Review B ; Volume 103, Issue 14 , 2021 ; 24699950 (ISSN) Sadrzadeh, M ; Jafari, R ; Langari, A ; Sharif University of Technology
    American Physical Society  2021
    The nonequilibrium dynamics of two-dimensional Su-Schrieffer-Heeger model, in the presence of staggered chemical potential, is investigated using the notion of dynamical quantum phase transition. We contribute to expanding the systematic understanding of the interrelation between the equilibrium quantum phase transition and the dynamical quantum phase transition (DQPT). Specifically, we find that dynamical quantum phase transition relies on the existence of massless propagating quasiparticles as signaled by their impact on the Loschmidt overlap. These massless excitations are a subset of all gapless modes, which leads to quantum phase transitions. The underlying two-dimensional model reveals... 

    Optimal acceptance sampling policy considering Bayesian risks

    , Article Communications in Statistics - Theory and Methods ; Volume 46, Issue 11 , 2017 , Pages 5228-5237 ; 03610926 (ISSN) Adibfar, S ; Fallah Nezhad, M. S ; Jafari, R ; Sharif University of Technology
    Taylor and Francis Inc  2017
    In this paper, we propose a sampling policy considering Bayesian risks. Various definitions of producer's risk and consumer's risk have been made. Bayesian risks for both producer and consumer are proven to give better information to decision-makers than classical definitions of the risks. So considering the Bayesian risk constraints, we seek to find optimal acceptance sampling policy by minimizing total cost, including the cost of rejecting the batch, the cost of inspection, and the cost of defective items detected during the operation. Proper distributions to construct the objective function of the model are specified. In order to demonstrate the application of the proposed model, we...