Browsing by Author "Klyachko, Alexander A."
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Item Open Access Entanglement and its operational measure(Springer, 2006) Klyachko, Alexander A.; Öztop, Barış; Shumovsky, Alexander S.An operational representation of concurrence measuring the entanglement of bipartite systems by means of averages of basic observables is discussed. We prove the validity of this representation for bipartite systems with any dimension of a single-party Hilbert space. We show that Wigner-Yanase "skew" information gives a reasonable estimation of the amount of entanglement (in ebits) carried by mixed two-qubit states.Item Open Access General entanglement(IOP, 2006) Klyachko, Alexander A.; Shumovsky, Alexander S.The paper contains a brief review of an approach to quantum entanglement based on analysis of dynamic symmetry of systems and quantum uncertainties, accompanying the measurement of mean value of certain basic observables. The latter are defined in terms of the orthogonal basis of Lie algebra, corresponding to the dynamic symmetry group. We discuss the relativity of entanglement with respect to the choice of basic observables and a way of stabilization of robust entanglement in physical systems.Item Open Access Persistent perfect entanglement in atomic systems(IOP, 2004) Çakır, Özgür; Can, M. Ali; Klyachko, Alexander A.; Shumovsky, Alexander S.It is shown that the system of an even number of three-level atoms in the Λ configuration in a cavity can evolve into a persistent maximum entangled state. The time of formation of such an entangled state is estimated.Item Open Access Quantifying quantum information via uncertainties(OSA, 2007) Öztop, Barış; Klyachko, Alexander A.; Shumovsky, Alexander S.We show, for a state ψ of a quantum system with the dynamic symmetry given by the Lie group G, total amount of quantum information and entanglement is provided by summarized uncertainty of basic observables.Item Open Access Quantum marginal problem and N-representability(IOP, 2006) Klyachko, Alexander A.A fermionic version of the quantum marginal problem was known from the early sixties as N-representability problem. In 1995 it was mentioned by the National Research Council of the USA as one of ten most prominent research challenges in quantum chemistry. In spite of this recognition the progress was very slow, until a couple of years ago the problem came into focus again, now in the framework of quantum information theory. In the paper I give a survey of the recent development.Item Open Access Single qutrit entanglement(OSA, 2007) Binicioğlu, Sinem; Klyachko, Alexander A.; Shumovsky, Alexander S.We discussed a recent approach to quantum entanglement. The approach is based on presetting of basic observables of quantum system. Entangled states are interpreted as states with maximal amount of uncertainty of all basic observables.Item Open Access Spin squeezing and entanglement(OSA, 2007) Öztop, Barış; Klyachko, Alexander A.; Shumovsky, Alexander S.We reformulate definition of spin squeezing and spin coherence in terms of the total variance in spin operators. We propose a new measure of spin squeezing. We show equivalence of spin squeezing and spin entanglement.