ua nt - p h / 01 02 04 0 v 2 1 0 Ju n 20 01 Universal state inversion and concurrence in arbitrary dimensions

ua nt - p h / 01 02 04 0 v 1 7 F eb 2 00 1 Universal state inversion and concurrence in arbitrary dimensions

Wootters [Phys. Rev. Lett. 80, 2245 (1998)] has given an explicit formula for the entanglement of formation of two qubits in terms of what he calls the concurrence of the joint density operator. Wootters’s concurrence is defined with the help of the superoperator that flips the spin of a qubit. We generalize the spin-flip superoperator to a “universal inverter,” which acts on quantum systems of...

/ 01 02 04 0 v 2 10 J un 2 00 1 Universal state inversion and concurrence in arbitrary dimensions

Wootters [Phys. Rev. Lett. 80, 2245 (1998)] has given an explicit formula for the entanglement of formation of two qubits in terms of what he calls the concurrence of the joint density operator. Wootters’s concurrence is defined with the help of the superoperator that flips the spin of a qubit. We generalize the spin-flip superoperator to a “universal inverter,” which acts on quantum systems of...

ua nt - p h / 01 02 07 0 v 1 1 3 Fe b 20 01 State Preparation and Some Applications in Quantum Optics within the context of Quantum Information Theory

ar X iv : q ua nt - p h / 05 03 10 3 v 1 1 0 M ar 2 00 5 Schwarz inequality and concurrence

We establish a relation between the Schwarz inequality and the generalized concurrence of an arbitrary, pure, bipartite or tripartite state. This relation places concurrence in a geometrical and functional-analytical setting.

ua nt - p h / 05 01 02 9 v 2 1 0 Ja n 20 05 Thermal Entanglement between Alternate Qubits of a Four - qubit Heisenberg XX Chain in a Magnetic Field

The concurrence of two alternate qubits in a four-qubit Heisenberg XX chain is investigated when a uniform magnetic field B is included. It is found that there is no thermal entanglement between alternate qubits if B is close to zero. Magnetic field can induce entanglement in a certain range both for the antiferromagnetic and ferromagnetic cases. Near zero temperature, the entanglement undergoe...