Generating coherent state of entangled spins

A coherent state of many spins contains quantum entanglement which increases with a decrease in the collective spin value. We present a scheme to engineer this class of pure state based on incoherent spin pumping with a few collective raising/lowering operators. In a pumping scenario aimed for maximum entanglement, the steady-state of N pumped spin qubits realizes the ideal resource for the 1 to N/2 quantum telecloning. We show how the scheme can be implemented in a realistic system of atomic spin qubits in optical lattice. Error analysis show that high fidelity state engineering is possible for N ~ O(100) spins in the presence of decoherence. The scheme can also prepare a resource state for the secret sharing protocol and for the construction of large scale Affleck-Kennedy-Lieb-Tasaki (AKLT) state.Comment: updated version to appear on Phys. Rev.

Oblique Corrections in the MSSM at One Loop. I. Scalars

This paper is devoted to reconsider the one-loop oblique corrections arising from the scalar superpartners in the MSSM, i.e, the squarks, the sleptons and the scalars in Higgs sector. We explicitly present the complete one-loop forms of self-energy corrections to the gauge bosons of SM electroweak gauge groups, as well as their descendants the $S$, $T$ and $U$ parameters, which can be directly applied to constrain the parameter space of the MSSM. Our results about one-loop self energies are found to agree with Drees, Hagiwara, and Yamada (1992), Pierce et al. (1997). Nevertheless, the $S$, $T$ and $U$ parameters aren't in agreement with Dobado, Herrero and Penaranda (1999).Comment: short version to appear in Advances in High Energy Physic