Institute for Physical Research

NASRA, Armenia

Institute for Physical Research

NASRA, Armenia
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Chakhmakhchyan L.,University of Burgundy | Chakhmakhchyan L.,Institute for Physical Research | Chakhmakhchyan L.,Ai Alikhanyan National Science Laboratory | Leroy C.,University of Burgundy | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

We consider systems of two and three qubits, mutually coupled by Heisenberg-type exchange interaction and interacting with external laser fields. We show that these systems allow one to create maximally entangled Bell states, as well as three-qubit Greenberger-Horne-Zeilinger and W states. In particular, we point out that some of the target states are the eigenstates of the initial bare system. Due to this, one can create entangled states by means of pulse area and adiabatic techniques, when starting from a separable (nonentangled) ground state. On the other hand, for target states, not present initially in the eigensystem of the model, we apply the robust stimulated Raman adiabatic passage and π pulse techniques, that create desired coherent superpositions of nonentangled eigenstates. © 2014 American Physical Society.

Chakhmakhchyan L.,Ai Alikhanyan National Science Laboratory | Chakhmakhchyan L.,Laboratory Interdisciplinaire Carnot de Bourgogne | Chakhmakhchyan L.,Institute for Physical Research | Shepelyansky D.,French National Center for Scientific Research
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

We consider a PageRank model of opinion formation on Ulam networks, generated by the intermittency map and the typical Chirikov map. The Ulam networks generated by these maps have certain similarities with such scale-free networks as the World Wide Web (WWW), showing an algebraic decay of the PageRank probability. We find that the opinion formation process on Ulam networks has certain similarities but also distinct features comparing to the WWW. We attribute these distinctions to internal differences in network structure of the Ulam and WWW networks. We also analyze the process of opinion formation in the frame of generalized Sznajd model which protects opinion of small communities. © 2013 Elsevier B.V.

Chakhmakhchyan L.,Laboratory Interdisciplinaire Carnot de Bourgogne | Chakhmakhchyan L.,Institute for Physical Research | Chakhmakhchyan L.,Ai Alikhanyan National Science Laboratory | Guerin S.,Laboratory Interdisciplinaire Carnot de Bourgogne | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

We adopt the beam-splitter model for losses to analyze the performance of a recent compact continuous-variable entanglement distillation protocol implemented using realistic quantum memories. We show that the decoherence undergone by a two-mode squeezed state while stored in a quantum memory can strongly modify the results of the preparatory step of the protocol. We find that the well-known method for locally increasing entanglement, phonon subtraction, may not result in entanglement gain when losses are taken into account. Thus, we investigate the critical number mc of phonon subtraction attempts from the matter modes of the quantum memory. If the initial state is not de-Gaussified within mc attempts, the protocol should be restarted to obtain any entanglement increase. Moreover, the condition m c>1 implies an additional constraint on the subtraction beam-splitter interaction transmissivity, viz., it should be about 50% for a wide range of protocol parameters. Additionally, we consider the average entanglement rate, which takes into account both the unavoidable probabilistic nature of the protocol and its possible failure as a result of a large number of unsuccessful subtraction attempts. We find that a higher value of the average entanglement can be achieved by increasing the subtraction beam-splitter interaction transmissivity. We conclude that the compact distillation protocol with the practical constraints coming from realistic quantum memories allows a feasible experimental realization within existing technologies. © 2013 American Physical Society.

Ananikian N.S.,A i Alikhanyan National Science Laboratory | Ananikian N.S.,Federal University of Lavras | Ananikyan L.N.,A i Alikhanyan National Science Laboratory | Chakhmakhchyan L.A.,A i Alikhanyan National Science Laboratory | And 3 more authors.
Journal of Physics Condensed Matter | Year: 2012

The entanglement quantum properties of a spin-1/2 IsingHeisenberg model on a symmetrical diamond chain were analyzed. Due to the separable nature of the Ising-type exchange interactions between neighboring Heisenberg dimers, calculation of the entanglement can be performed exactly for each individual dimer. Pairwise thermal entanglement was studied in terms of the isotropic IsingHeisenberg model and analytical expressions for the concurrence (as a measure of bipartite entanglement) were obtained. The effects of external magnetic field H and next-nearest neighbor interaction J m between nodal Ising sites were considered. The ground state structure and entanglement properties of the system were studied in a wide range of coupling constant values. Various regimes with different values of ground state entanglement were revealed, depending on the relation between competing interaction strengths. Finally, some novel effects, such as the two-peak behavior of concurrence versus temperature and coexistence of phases with different values of magnetic entanglement, were observed. © 2012 IOP Publishing Ltd.

Chakhmakhchyan L.,Ai Alikhanyan National Science Laboratory | Chakhmakhchyan L.,Institute for Physical Research | Ananikian N.,Ai Alikhanyan National Science Laboratory | Ananikyan L.,Ai Alikhanyan National Science Laboratory | Burdik C.,Czech Technical University
Journal of Physics: Conference Series | Year: 2012

The entanglement thermal (equilibrium) properties in spin-1/2 Ising-Heisenberg model on an ideal diamond chain is analyzed. Due to the classical character of Ising-type exchange interactions between two neighboring antiferromagnetic Heisenberg dimers, the calculation of quantum entanglement (by tracing out Ising spins) can be performed for each of the dimers separately. The concurrence, as a measure of entanglement is obtained and different regimes depending on the values of exchange interactions are revealed. The effects of the magnetic field are incorporated and critical temperatures corresponding to the vanishing or arising of entanglement are considered.

Abovyan G.A.,Yerevan State University | Abovyan G.A.,Institute for Physical Research | Djotyan G.P.,Hungarian Academy of Sciences | Kryuchkyan G.Y.,Yerevan State University | Kryuchkyan G.Y.,Institute for Physical Research
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

The deflection of atoms in a Λ-type configuration passing through two crossed standing light waves is proposed for the probing and visualization of atomic superposition states. For this goal, we use both the large-dispersive and Raman-resonant regimes of atom-field interaction, giving rise to position-dependent phase shifts of fields, and perform double simultaneous spatial measurements on an atom. In this way, it is demonstrated that the deflection spatial patterns of atoms in a Λ-configuration passing through modes of standing waves are essentially modified if the atoms are initially prepared in coherent superpositions of their low-level states as well as when the superposition states are created during the process of deflection. There are similar results for the joint momentum distributions of atoms. Furthermore, considering both one-photon- and two-photon-excitation regimes of Λ atoms, we also illustrate that the two-dimensional patterns of defected atoms qualitatively reflect the efficiency of the Raman processes. © 2012 American Physical Society.

Abovyan G.A.,Institute for Physical Research | Kryuchkyan G.Y.,Yerevan State University
Journal of the Optical Society of America B: Optical Physics | Year: 2016

We study qubit manipulations by a train of pulses in a systematic approach based on the Magnus expansion and Furry representation in quantum electrodynamics. Furry-Magnus expansion gives approximate exponential representation of a time-evolution operator without the Dyson time-ordering procedure for interactions with external fields of arbitrary intensity and allows us to obtain general expression for single-qubit populations as a function of time-dependent Rabi frequency. The concrete calculations are performed for tunneling quantum dynamics, for multiphoton resonance interactions of qubits, as well as for off-resonance excitations of qubits driven by Gaussian pulses beyond rotating wave approximation. In this way, the populations of qubit states are investigated for various operational regimes, including single-pulse excitation and two-pulse excitation with a phase shift between pulse envelopes being the controlling parameter, and for excitation with sequential pulses. In the last case, we demonstrate the formation of quasi-energetic states and quasi-energies of qubits driven by a train of identical pulses. In this case the transition probability of the qubit generally exhibiting aperiodic oscillations becomes periodically regular for definite values of the quasi-energy. © 2016 Optical Society of America.

Sargsyan A.,Institute for Physical Research | Hakhumyan G.,Institute for Physical Research | Leroy C.,Laboratory Interdisciplinaire Carnot de Bourgogne | Pashayan-Leroy Y.,Laboratory Interdisciplinaire Carnot de Bourgogne | And 3 more authors.
Journal of the Optical Society of America B: Optical Physics | Year: 2014

Simple and efficient λ-method and λ?2-method (λ is the resonant wavelength of laser radiation) based on a nanometric-thickness cell filled with rubidium (Rb) are implemented to study the splitting of hyperfine transitions of an 85Rb and 87Rb D1 line in an external magnetic field in the range of B0.5-0.7 T. It is experimentally demonstrated from 20 (12) Zeeman transitions allowed at low B-field in 85Rb (87Rb) spectra in the case of δ+ polarized laser radiation, only 6 (4) remain atB > 0.5 T, caused by decoupling of the total electronic momentum J and the nuclear spin momentum I (hyperfine Paschen-Back regime). The expressions derived in the frame of completely uncoupled basis (J;mJ ; I;mI ) describe the experimental results extremely well for 85Rb transitions at B > 0.6 T (that is a manifestation of hyperfine Paschen-Back regime). A remarkable result is that the calculations based on the eigenstates of the coupled (F;mF ) basis, which adequately describe the system for a low magnetic field, also predict reduction of the number of transition components from 20 to 6 for 85Rb and from 12 to 4 for 87Rb spectrum at B > 0.5 T. Also, the Zeeman transition frequency shifts, frequency intervals between the components and their slope versus B, are in agreement with the experiment. © 2014 Optical Society of America.

Kuzanyan A.A.,Institute for Physical Research | Kuzanyan A.S.,Institute for Physical Research | Nikoghosyan V.R.,Institute for Physical Research
Journal of Physics: Conference Series | Year: 2016

The results of computer simulation of heat distribution on the sensor of Thermoelectric Single Photon Detector after photon absorption are presented in this work. The kinetic processes emerging after the absorption of 100 eV (hard UV) and 1 KeV (X-ray) energy photons in different areas of the absorber for different sensor and absorber geometries are investigated. The calculations were performed for the tungsten absorber and the cerium hexaboride sensor. It is shown, that waveform of time dependence of response doesn't strongly depend from the depth of photon thermalization area in absorber and the height on which the temperature gradient on the edges of thermoelectric sensor is measured.

Kuzanyan A.S.,Institute for Physical Research | Kuzanyan A.A.,Institute for Physical Research
NSTI: Advanced Materials - TechConnect Briefs 2015 | Year: 2015

Simple and inexpensive methods of obtaining large area uniform in thickness and composition thin films on large and very large rotating substrates and moving ribbons through pulsed laser deposition have been proposed. Thin films of different composition were deposited with these methods. The thickness uniformity of films obtained with these methods was preserved within the limits of ±3% on up to 300 mm diameter substrates. Also a method of creating a laser spot of a certain configuration on the target is proposed, allowing almost full utilization of the target material.

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