23,351 research outputs found
IUE observations of blue halo high luminosity stars
Two high luminosity population II blue stars of high galactic latitude, BD+33 deg 2642 and HD 137569 were observed at high resolution. The stellar spectra show the effect of mass loss in BD+33 deg 2642 and abnormally weak metallic lines in HD 137569. The interstellar lines in the direction of BD+33 deg 2642, which lies at a height z greater than or equal to 6.2 kpc from the galactic plane, are split into two components. No high ionization stages are found at the low velocity component; nor can they be detected in the higher velocity clouds because of mixing with the corresponding stellar/circumstellar lines
Factorization, charming penguins, and all that
We discuss few selected topics related to the calculation of hadronic
amplitudes relevant for two-body non-leptonic B decays.Comment: LaTeX, 9 pages, 1 eps figure included, uses psfig.sty. Talk given by
M.C. at Beauty '97, UCLA, USA, October 13-17, 199
Controllable coherent population transfers in superconducting qubits for quantum computing
We propose an approach to coherently transfer populations between selected
quantum states in one- and two-qubit systems by using controllable
Stark-chirped rapid adiabatic passages (SCRAPs). These {\it evolution-time
insensitive} transfers, assisted by easily implementable single-qubit
phase-shift operations, could serve as elementary logic gates for quantum
computing. Specifically, this proposal could be conveniently demonstrated with
existing Josephson phase qubits. Our proposal can find an immediate application
in the readout of these qubits. Indeed, the broken parity symmetries of the
bound states in these artificial "atoms" provide an efficient approach to
design the required adiabatic pulses.Comment: 4 pages, 6 figures. to appear in Physical Review Letter
Enhancing the conductance of a two-electron nanomechanical oscillator
We consider electron transport through a mobile island (i.e., a
nanomechanical oscillator) which can accommodate one or two excess electrons
and show that, in contrast to immobile islands, the Coulomb blockade peaks,
associated with the first and second electrons entering the island, have
different functional dependences on the nano-oscillator parameters when the
island coupling to its leads is asymmetric. In particular, the conductance for
the second electron (i.e., when the island is already charged) is greatly
enhanced in comparison to the conductance of the first electron in the presence
of an external electric field. We also analyze the temperature dependence of
the two conduction peaks and show that these exhibit different functional
behaviors.Comment: 16 pages, 5 figure
Dynamics of Entanglement and Bell-nonlocality for Two Stochastic Qubits with Dipole-Dipole Interaction
We have studied the analytical dynamics of Bell nonlocality as measured by
CHSH inequality and entanglement as measured by concurrence for two noisy
qubits that have dipole-dipole interaction. The nonlocal entanglement created
by the dipole-dipole interaction is found to be protected from sudden death for
certain initial states
Time resolved structural dynamics of butadiyne-linked porphyrin dimers
In this work the timescales and mechanisms associated with the structural dynamics of butadiyne-linked porphyrin dimers are investigated through time resolved narrowband pump / broadband probe transient absorption spectroscopy. Our results confirm previous findings that the broadening is partly due to a distribution of structures with different (dihedral) angular conformations. Comparison of measurements with excitations on the red and blue sides of the Q-band unravel the ground and excited state conformational re-equilibration timescales. Further comparison to a planarized dimer, through addition of a ligand, provide conclusive evidence for the twisting motion performed by the porphyrin dimer in solution
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