Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection

Permanent URI for this collectionhttps://hdl.handle.net/11147/7148

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  • Conference Object
    Geometry and Entanglement of Super-Qubit Quantum States
    (Springer International Publishing AG, 2025) Pashaev, Oktay K.; Kocak, Aygul
    We introduce the super-qubit quantum state, determined by superposition of the zero and the one super-particle states, which can be represented by points on the super-Bloch sphere. In contrast to the one qubit case, the one super-particle state is characterized by points in extended complex plane, equivalent to another super-Bloch sphere. Then, geometrically, the super-qubit quantum state is represented by two unit spheres, or the direct product of two Bloch spheres. By using the displacement operator, acting on the super-qubit state as the reference state, we construct the super-coherent states, becoming eigenstates of the super-annihilation operator, and characterized by three complex numbers. The states are fermion-boson entangled, and the concurrence of states is the product of two concurrences, corresponding to two Bloch spheres. We show geometrical meaning of concurrence as distance from point-state on the sphere to vertical axes. Then, probabilities of collapse to the north pole state and to the south pole state are equal to half-distances from vertical coordinate of the state to corresponding points at the poles. For complimentary fermion number operator, we get the flipped super-qubit state and corresponding super-coherent state, as eigenstate of transposed super-annihilation operator. The infinite set of Fibonacci oscillating circles in complex plane, describing quantum states with uncertainty relations as the ratio of two Fibonacci numbers, and in the limit at infinity becoming the Golden Ration uncertainty, is derived.
  • Article
    Quantum Calculus of Fibonacci Divisors and Fermion-Boson Entanglement for Infinite Hierarchy of N=2 Supersymmetric Golden Oscillators
    (Pleiades Publishing Ltd, 2025) Pashaev, O. K.
    The quantum calculus with two bases, represented by powers of the golden and silver ratios, relates the Fibonacci divisor derivative with Binet formula for the Fibonacci divisor number operator, acting in the Fock space of quantum states. It provides a tool to study the hierarchy of golden oscillators with energy spectrum in the form of Fibonacci divisor numbers. We generalize this model to the supersymmetric number operator and corresponding Binet formula for the supersymmetric Fibonacci divisor number operator. The operator determines Hamiltonian of the hierarchy of supersymmetric golden oscillators, acting in fermion-boson Hilbert space and belonging to N = 2 supersymmetric algebra. The eigenstates of the super Fibonacci divisor number operator are double degenerate and can be characterized by a point on the super-Bloch sphere. By introducing the supersymmetric Fibonacci divisor annihilation operator, we construct the hierarchy of supersymmetric coherent states as eigenstates of this operator. The entanglement of fermions with bosons in these states is calculated by the concurrence, represented as the Gram determinant and expressed in terms of the hierarchy of golden exponential functions. We show that the reference states and the corresponding von Neumann entropy measuring the fermion-boson entanglement are characterized completely by powers of the golden ratio. We give a geometrical classification of entangled states by the Frobenius ball and interpret the concurrence as the double area of a parallelogram in a Hilbert space.
  • Article
    Effective Geometry of Bell-Network States on a Dipole Graph
    (Institute of Physics, 2025) Baytaş, B.; Yokomizo, N.
    Bell-network states are a class of entangled states of the geometry that satisfy an area-law for the entanglement entropy in a limit of large spins and are automorphism-invariant, for arbitrary graphs. We present a comprehensive analysis of the effective geometry of Bell-network states on a dipole graph. Our main goal is to provide a detailed characterization of the quantum geometry of a class of diffeomorphism-invariant, area-law states representing homogeneous and isotropic configurations in loop quantum gravity, which may be explored as boundary states for the dynamics of the theory. We found that the average geometry at each node in the dipole graph does not match that of a flat tetrahedron. Instead, the expected values of the geometric observables satisfy relations that are characteristic of spherical tetrahedra. The mean geometry is accompanied by fluctuations with considerable relative dispersion for the dihedral angle, and perfectly correlated for the two nodes. © 2024 IOP Publishing Ltd. All rights, including for text and data mining, AI training, and similar technologies, are reserved.
  • Conference Object
    Citation - Scopus: 2
    Maximally Entangled Two-Qutrit Quantum Information States and De Gua’s Theorem for Tetrahedron
    (Springer, 2023) Pashaev, Oktay
    Geometric relations between separable and entangled two-qubit and two-qutrit quantum information states are studied. For two qubit states a relation between reduced density matrix and the concurrence allows us to characterize entanglement by double area of a parallelogram, expressed by determinant of the complex Hermitian inner product metric. We find similar relation in the case of generic two-qutrit state, where the concurrence is expressed by sum of all 2 × 2 minors of 3 × 3 complex matrix. We show that for maximally entangled two-retrit state this relation is just De Gua’s theorem or a three-dimensional analog of the Pythagorean theorem for triorthogonal tetrahedron areas. Generalizations of our results for arbitrary two-qudit states are discussed © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.
  • Article
    Citation - WoS: 11
    Citation - Scopus: 10
    Entanglement in Two Qubit Magnetic Models With Dm Antisymmetric Anisotropic Exchange Interaction
    (World Scientific Publishing Co. Pte Ltd, 2010) Gürkan, Zeynep Nilhan; Pashaev, Oktay
    In the present paper, an influence of the anisotropic antisymmetric exchange interaction, the DzialoshinskiiMoriya (DM) interaction, on entanglement of two qubits in various magnetic spin models, including the pure DM model and the most general XYZ model, are studied. We find that the time evolution generated by DM interaction can implement the SWAP gate and discuss realistic quasi-one-dimensional magnets where it can be realized. It is shown that inclusion of the DM interaction to any Heisenberg model creates, when it does not exist, or strengthens, when it exists, the entanglement. We give physical explanation of these results by studying the ground state of the systems at T = 0. Nonanalytic dependence of the concurrence on the DM interaction and its relation with quantum phase transition is indicated. Our results show that spin models with the DM coupling have some potential applications in quantum computations and the DM interaction could be an efficient control parameter of entanglement. © 2010 World Scientific Publishing Company.