Browsing by Author "Shumovsky, A. S."
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Item Open Access Angular momentum of photons emitted by atoms(Institute of Physics Publishing Ltd., 2004) Can, M. A.; Çakır, Ö.; Horzela, A.; Kapuscik, E.; Klyachko, A. A.; Shumovsky, A. S.It is shown that the spin and orbital angular momentum of electric dipole photons have the same operator structure and may differ from each other only in the spatial dependence in the very vicinity of the atom. It is shown that the photon twins created by a dipole forbidden transition can manifest the maximum entanglement with respect to the angular momentum. It is shown that the states of photons with a projection of angular momentum m = 0 are less stable than those with m = ±1.Item Open Access Conditions for observation of Rabi oscillations in an exciton-polariton system(Elsevier BV, 1995) Shumovsky, A. S.; Müstecaplioǧlu, Ö. E.The pure quantum model describing Rabi oscillations of exciton-polaritons (EP) in a micro-cavity with finite quality is considered. It is shown that the oscillations can be observed if the cavity damping rate does not exceed some critical value depending on the EP coupling constant and the detuning of the cavity mode. An explicit expression for the renormalized Rabi frequency is found. Comparison of the results with experimental data shows a good agreement. © 1995.Item Open Access Detecting squeezed phonons through an indirect radiative transition(A I P Publishing LLC, 1997-04-27) MÜstecaplioglu, Ö. E.; Shumovsky, A. S.A model of the effect of the longitudinal optical phonon number distribution on the Rabi oscillations of the photons involved in the associated indirect transition in a semiconductor is presented. It is shown that a faster cavity photon revival rate is obtained given an initial squeezed thermal phonon state. This is the result of pairwise correlations of phonons due to squeezing and also holds true when phonons are in squeezed vacuum or in squeezed number states; It may be possible to use this effect to detect squeezing in phonons. (C) 1997 American Institute of Physics.Item Open Access Dual representation of dipole photons(Institute of Physics Publishing Ltd., 1999) Shumovsky, A. S.The quantum polarization and phase properties of an electric dipole radiation are examined. It is shown that, unlike the classical picture, the quantum description of polarization needs nine independent Stokes operators, forming a representation of SU (3) sub-algebra in the Weyl-Heisenberg algebra of photons. A corresponding Cartan algebra determines the cosine and sine of the radiation phase operators. A new representation of dipole photons is proposed. The generators of the Cartan algebra are diagonal in this representation so that the corresponding number states describe the number of photons with given radiation phase. The eigenstates of the radiation phase are determined. They have a discrete spectrum and natural behaviour in the classical limit. The relation between the radiation phase, operational phases and the Pegg-Barnett approach is discussed.Item Open Access Entanglement and the SU(2) phase states in atomic systems(American Physical Society, 2002) Can, M. A.; Klyachko, A. A.; Shumovsky, A. S.For the system of two identical two-level atoms interacting with a single photon, it is shown that the maximum entangled atomic states are represented by the SU(2) phase states of spin 1/2. Furthermore, it is shown that the SU(2) phase states of the half-integer spin j for a certain class of maximum entangled atomic states in the system of 2n atoms interacting with n photons. In particular, the violation of classical realism is shown.Item Open Access Entanglement of a single spin-1 object: An example of ubiquitous entanglement(Springer New York LLC, 2007) Binicioǧlu, S.; Can, M. A.; Klyachko, A. A.; Shumovsky, A. S.Using a single spin-1 object as an example, we discuss a recent approach to quantum entanglement. [A.A. Klyachko and A.S. Shumovsky, J. Phys: Conf. Series 36, 87 (2006), E-print quant-ph/0512213]. The key idea of the approach consists in presetting of basic observables in the very definition of quantum system. Specification of basic observables defines the dynamic symmetry of the system. Entangled states of the system are then interpreted as states with maximal amount of uncertainty of all basic observables. The approach gives purely physical picture of entanglement. In particular, it separates principle physical properties of entanglement from inessential. Within the model example under consideration, we show relativity of entanglement with respect to dynamic symmetry and argue existence of single-particle entanglement. A number of physical examples are considered.Item Open Access Entanglement of qutrits(Institute of Physics Publishing Ltd., 2007) Klyachko, A. A.; Öztop, B.; Shumovsky, A. S.For two types of qutrits specified by the dynamical symmetry SU(3) and SU(2), we consider the difference in entanglement caused by the lack of quantum observables in the latter case. In particular, we show that the SU(2) qutrits can have specific separable entanglement caused by quantum correlations of intrinsic degrees of freedom in a single party without interparty correlations. © Nauka/Interperiodica 2007.Item Open Access Entanglement, local measurements and symmetry(Institute of Physics Publishing, 2003) Klyachko, A. A.; Shumovsky, A. S.AbstractAdefinition of entanglement in terms of local measurements is discussed.Namely, the maximum entanglement corresponds to the states that cause thehighest level of quantum fluctuations in all local measurements determinedby the dynamic symmetry group of the system. A number of examplesillustrating this definition is consideredItem Open Access General approach to quantum entanglement(Institute of Physics Publishing Ltd., 2007) Klyachko, A. A.; Shumovsky, A. S.We examine quantum entanglement as a physical phenomenon independent of specific problems of quantum information technologies. Within the dynamic symmetry approach, we briefly discuss the role of quantum fluctuations in formation of entangled states, including single-particle entanglement, relativity of entanglement with respect to the choice of basic observables, and stabilization of robust entanglement.Item Open Access Generic entangled states as the su(2) phase states(World Scientific Publishing, 2005) Binicioǧlu, S.; Çakir, Ö.; Klyachko, A. A.; Shumovsky, A. S.We discuss an algebraic way to construct generic entangled states of qunits based on the polar decomposition of the su(2) algebra. In particular, we show that these states can be defined as eigenstates of certain Hermitian operators.Item Restricted Maximum entanglement(Institute of Physics Publishing, 2003-08) Klyachko, A. A.; Shumovsky, A. S.We discuss a novel variational principle in quantummechanics defining maximum entangled states in terms of quantum fluctuations of observables specifying these stales.Item Open Access Maximum entanglement and its proper measure(Institute of Physics, 2004) Klyachko, A. A.; Shumovsky, A. S.We discuss a definition of maximally entangled states in terms of maximum uncertainty of corresponding measurements. We describe a method of construction of bases of maximally entangled states. The entangled states that can be obtained from the maximally entangled states by means of SLOCC (stochastic local operations assisted by classical communications) we consider as semistable vectors. We discuss a measure of entanglement expressed in terms of a geometric invariant.Item Open Access Measurable entanglement(2006) Klyachko, A.; Öztop, B.; Shumovsky, A. S.The amount of entanglement carried by a quantum bipartite state is usually evaluated in terms of concurrence [S. Hill and W. K. Wootters, Phys. Rev. Lett. 78, 5022 (1997); P. Rungta, V. Bužek, C. M. Caves, M. Hillery, and G. J. Milburn, Phys. Rev. A 64, 042315 (2001)]. We give a physical interpretation of concurrence that reveals a way of its direct measurement and discuss possible generalizations. © 2006 American Institute of Physics.Item Open Access Observables, quantum fluctuations,and “quantum reality”(Horizon Research Publishing, 2004) Shumovsky, A. S.AbstractWe discuss difference between the classical and quantummethods of description of Nature in terms of fundamentalobservables related to the dynamical symmetry group of theHilbert space and quantum fluctuations, specifying their mea-surement. We show that the total amount of quantum fluc-tuations of fundamental observables can be used to measurethe “remoteness” of quantum states from “classical reality”provided by the choice of observables in terms of c-numbers.The proposed picture is more general than Bell’s approach todefinition of “classical reality”.Item Open Access Operational approach to quantum limits on polarization measurement(Elsevier, 1994) Hakioğlu, T.; Shumovsky, A. S.; Aytür, O.We discuss the polarization measurement of a fully polarized coherent field in the weak intensity quantum limit within the framework of operational approach which was recently discussed by Noh, Fougéres and Mandel. We mainly focus on the fluctuations in the measurement of the parameters of polarization and on the uncertainty relations between them. A dependence of these parameters and their quantum fluctuations on the parameters of the initial coherent field is found. © 1994.Item Open Access Operational measure of entanglement for pure states of bipartite systems(Akademiai Kiado Rt., 2006-03) Klyachko, A. A.; Öztop, B.; Shumovsky, A. S.We show that the complete information about the amount of entanglement carried by a bipartite pure state of any dimension (qubits, qutrits, etc), is determined by a local quantity that can be measured for either party of the system. This quantity is expressed in terms of averages of certain basic observables. In particular case of two entangled photon beams, this corresponds to the measurement of three Stokes parameters for either beam.Item Open Access Persistent perfect entanglement in atomic systems(Institute of Physics Publishing, 2004) Çakir, Ö.; Can, M. A.; Klyachko, A. A.; Shumovsky, A. S.It is show that the system of an even number of three-level atoms in the A configuration in a cavity can evolve into a persistent maximum entangled state. The time of formation or such an entangled state is estimated.Item Open Access Phonon squeezing in superconducting borocarbides(Elsevier BV * North-Holland, 1994) Hakioglu, T.; Ivanov, V. A.; Shumovsky, A. S.; Tanatar, BilalThe recently discovered superconductor LuNi2B2C is investigated in the context of strong electron-electron correlations modulated by a squeezed phonon mode propagating in the perpendicular direction to the layers with longitudinal polarization. The squeezed phonons arise in the anharmonic lattice expansion since the linear electron-phonon interaction vanishes due to the structure of the NiB4 tetrahedra. The observed weak isotope effect and small dependence of Tc on pressure is qualitatively understood within the framework of this model. © 1994.Item Open Access Phonon squeezing via correlations in the superconducting electron-phonon interaction(American Physical Society, 1995) Hakioğlu, T.; Ivanov, V. A.; Shumovsky, A. S.; Tanatar, BilalSuperconductivity in the conventional BCS model with correlated squeezed phonons is discussed. It is shown that the energy gap and the critical temperature are maximally enhanced in an optimum and finite range of squeezed coupling. For finite-squeezed coupling the ratio 2Δ/Tc becomes coupling-constant dependent and increases beyond the BCS value of 3.53. Ion-mass dependence of the squeezed coupling constant can yield variations of the isotope exponent from its conventional BCS value of 0.5. © 1995 The American Physical Society.Item Open Access Polarization of dipole radiation in quantum domain(American Physical Society, 1998) Shumovsky, A. S.; Müstecaplıoǧlu, Ö. E.For a dipole radiation, the set of generalized Stokes parameters and corresponding Stokes operators are discussed. A qualitatively new behavior of quantum fluctuations of the Stokes parameters is predicted. The possibility to check this behavior in the eight-port operational measurement is shown.