We suggest two schemes to generate bipartite entangled states by means of a quantum measurement at a third party. The two parties to be entangled have separate entangled states with the third party in modes C1 and C2. In our first scheme we generate entanglement between the two remote parties by considering the modes C1 and C2 indistinguishable. However, in the second scheme we generate entangled states by considering the two modes to be distinguishable. We discuss that the first scheme of remote entanglement generation can be extended to any N number of parties. On making a quantum measurement on this system, we develop quantum networks, based on W-states and other multipartite symmetric entangled states.

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Journal: Adv. Studies Theor. Phys., Vol. 5, 2011, no. 15, 733 - 742

Within the zero-temperature linear spin-wave theory we have investigated the effect of frustration and dimerization of a Heisenberg system with alternating spins s1 and s2 on one-and two dimensional lattices. The combined effect appears most visibly in the elementary excitation spectra. In contrast to the ground-state energy that decreases with dimerization and increases with frustration, the excitation energies are shown to be suppressed in energy by both dimerization and frustration. The excitation modes also exhibit softening beyond a threshold value of frustration, signalling a transition from a classical ferrimagnetic state to a spiral state. The threshold value of frustration in a chain decreases with dimerization, showing that dimerization further assists in the phase transition. That the long-range classical ferrimagnetic order is destroyed is shown by the correlation length as well as sublattice magnetization decreasing with both dimerization and frustration. These effects have also been studied for a square lattice taking the dimerization interaction asJ/(1 ∓ δ) rather than J(1±δ) where the linear spin-wave theory shows that dimerization initially opposes the frustrationled transition to a spiral magnetic state, but then higher magnitudes of lattice deformation facilitate the transition.

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Journal: J. Phys.: Condens. Matter 12 (2000) 1–14.

Quantum Dots (QDs) are semiconductor-nanostructure materials which are also called artificial atoms. QDs are classified as ferromagnetic material. Theoretically, Heisenberg model is regarded as a good model in describing these QDs. We applied Spin Wave Theory (SWT) on the above mentioned model to explore the physical properties of these materials, such as ground state energy, excitation energy and magnetization. We found that the ground state energy "g increased with the applied external magnetic field B as B0:3. A phase transition was also observed around B~1T, which indicate a transition from singlet to a triplet state. Staggered magnetization reaches saturation around this point of transition.

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Journal: EPH - International Journal of Applied Science

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