32 research outputs found
High-fidelity local addressing of trapped ions and atoms by composite sequences of laser pulses
A vital requirement for a quantum computer is the ability to locally address,
with high fidelity, any of its qubits without affecting their neighbors. We
propose an addressing method using composite sequences of laser pulses, which
reduces dramatically the addressing error in a lattice of closely spaced atoms
or ions, and at the same time significantly enhances the robustness of qubit
manipulations. To this end, we design novel high-fidelity composite pulses for
the most important single-qubit operations. In principle, this method allows
one to beat the diffraction limit, for only atoms situated in a small spatial
region around the center of the laser beam are excited, well within the laser
beam waist.Comment: Optics Letters Vol. 36, No. 7 (2011
Highly efficient broadband conversion of light polarization by composite retarders
Driving on an analogy with the technique of composite pulses in quantum
physics, we propose highly efficient broadband polarization converters composed
of sequences of ordinary retarders rotated at specific angles with respect to
their fast-polarization axes.Comment: 5 pages, 3 figures; check JOSA A 201
Solid-State Dynamics in the closo-Carboranes:A (11)B MAS NMR and Molecular Dynamics Study
This work explores the dynamic behaviour of the three closo-carborane isomers (formula C2B10H12) using modern solid-state magic angle spinning (MAS) NMR techniques and relates the experimental measurements to theoretical results obtained using molecular dynamics simulations. At high temperatures and at B0 = 9.4 T, the 11B MAS linewidths are narrow (40-90 Hz) for the three isomers. The rotational correlation times (tauc) calculated by molecular dynamics are on the picosecond timescale, showing a quasi-isotropic rotation at these temperatures, typical for liquid systems. For all three isomers, the values of the 11B spin-lattice relaxation times (T1) show discontinuities as the temperature is decreased, confirming the phase changes reported in the literature. At low temperatures, the 11B MAS spectra of all three isomers exhibit much broader lines. The simulations showed that the molecular reorientation was anisotropic around different symmetry axes for each isomer, and this was supported by the values of the reduced quadrupolar parameter PQeff derived from “dynamic shift” measurements using 11B MQMAS NMR spectroscopy. The behaviour of PQeff as a function of temperature for para-carborane suggests that molecular reorientation is about the C5 symmetry axis of the molecule at low temperatures and this was supported by the molecular dynamics simulations