nt - p h / 01 02 03 8 v 1 6 F eb 2 00 1 Quasiprobability and Probability Distributions for Spin 1 / 2 States ∗

nt - p h / 03 02 02 8 v 1 4 F eb 2 00 3 Quantum Tomography

ua nt - p h / 02 02 03 0 v 1 5 F eb 2 00 2 Quantum Computer with Fixed Interaction is Universal

It is proved that a quantum computer with fixed and permanent interaction of diagonal type between qubits proposed in the work quant-ph/0201132 is universal. Such computer is controlled only by one-qubit quick transformations, and this makes it feasible.

ar X iv : h ep - p h / 03 02 01 8 v 1 4 F eb 2 00 3 Saturation of optimality limits in hadron - hadron scatterings

In this paper the optimal unitarity lower bound on logarithmic slope of the diffraction peak is investigated. It is shown that the unitarity lower bound is just the optimal logarithmic slopes predicted by the principle of least distance in space of states. A systematic tendency towards the saturation of the most forward-peaked limit is observed from all the available experimental data of all pr...

nt - p h / 02 03 01 1 v 1 4 M ar 2 00 2 On the Entanglement Properties of Two - Rebits Systems

Following the recent work of Caves, Fuchs, and Rungta [Found. of Phys. we discuss some entanglement properties of two-rebits systems. We pay particular attention to the relationship between entangle-ment and purity. In particular, we determine (i) the probability densities for finding pure and mixed states with a given amount of entanglement, and (ii) the mean entanglement of two-rebits states ...

ua nt - p h / 01 02 02 5 v 1 5 F eb 2 00 1 Teleportation with indistinguishable particles . ∗

We analyze in a critical way the mathematical treatment of a quantum teleportation experiment performed with photon particles, showing that a symmetrization operation over both the polarization and spatial degrees of freedom of all the particles involved is necessary in order to reproduce correctly the observed experimental data.