nt - p h / 04 11 17 7 v 1 24 N ov 2 00 4 Engineering antiferromagnetic Heisenberg spin chains for maximizing of the groundstate entanglement

ua nt - p h / 04 07 07 3 v 3 2 5 N ov 2 00 4 Thermal entanglement of spins in an inhomogeneous magnetic field

We study the effect of inhomogeneities in the magnetic field on the thermal entanglement of a two spin system. We show that in the ferromagnetic case a very small inhomogeneity is capable to produce large values of thermal entanglement. This shows that the absence of entanglement in the ferromagnetic Heisenberg system is highly unstable against inhomogeneoity of magnetic fields which is inevita...

ar X iv : q ua nt - p h / 04 11 17 2 v 1 2 3 N ov 2 00 4 Information and Entropy in Quantum Theory

ua nt - p h / 04 05 06 0 v 5 2 5 N ov 2 00 4 Thermal entanglement of spins in the Heisenberg model at low temperatures

We calculate the entanglement between two spins in the ferromagnetic Heisen-berg chain at low temperatures, and show that when only the ground state and the one particle states are populated, the entanglement profile is a gaussian with a characteristic length depending on the temperature and the coupling between spins. The magnetic field only affects the amplitude of the profile and not its cha...

ar X iv : q ua nt - p h / 06 11 18 7 v 1 1 7 N ov 2 00 6 Philosophical Aspects of Quantum Information Theory

2 First steps with quantum information 3 2.1 Bits and qubits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2 The no-cloning theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.3 Quantum cryptography . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3.1 Key Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4 Entanglement-as...

ua nt - p h / 05 11 04 7 v 1 6 N ov 2 00 5 Entanglement swapping , light cones and elements of reality

Recently, a number of two-participant all-versus-nothing Bell experiments have been proposed. Here, we give local realistic explanations for these experiments. We examine the scenario where a participant swaps his entanglement with two other participants and then is removed from the experiment; we also examine the scenario where two particles are in the same light cone, i.e. belong to a single ...