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511.
Riebe M Kim K Schindler P Monz T Schmidt PO Körber TK Hänsel W Häffner H Roos CF Blatt R 《Physical review letters》2006,97(22):220407
A crucial building block for quantum information processing with trapped ions is a controlled-NOT quantum gate. In this Letter, two different sequences of laser pulses implementing such a gate operation are analyzed using quantum process tomography. Fidelities of up to 92.6(6)% are achieved for single-gate operations and up to 83.4(8)% for two concatenated gate operations. By process tomography we assess the performance of the gates for different experimental realizations and demonstrate the advantage of amplitude-shaped laser pulses over simple square pulses. We also investigate whether the performance of concatenated gates can be inferred from the analysis of the single gates. 相似文献
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It is well documented that helices in proteins can decrease the pKa of residues located at the N-terminus, but the real nature of this perturbation remains unclear. In the present work, the origin of the effect of 3(10)- and alpha-polyalanine helices on the pKa of an N-terminal cysteine residue is examined in gas phase as well as in aqueous solution by means of density functional theory. In a systematic study of the helix dipole, the proton affinity (PA), and the pKa of the N-terminal cysteine, in relation to both the helix length and the strength of the hydrogen bonds between the helix backbone amides and the Sgamma of the N-terminal cysteine, a direct relation between the terminal hydrogen bonds and the pKa perturbation is revealed. 相似文献
514.
The combination technique for a two-dimensional convection-diffusion problem with exponential layers
Sebastian Franz Fang Liu Hans-Görg Roos Martin Stynes Aihui Zhou 《Applications of Mathematics》2009,54(3):203-223
Convection-diffusion problems posed on the unit square and with solutions displaying exponential layers are solved using a
sparse grid Galerkin finite element method with Shishkin meshes. Writing N for the maximum number of mesh intervals in each
coordinate direction, our “combination” method simply adds or subtracts solutions that have been computed by the Galerkin
FEM on and meshes. It is shown that the combination FEM yields (up to a factor ln N) the same order of accuracy in the associated energy norm as the Galerkin FEM on an N × N mesh, but it requires only (N
3/2) degrees of freedom compared with the (N
2) used by the Galerkin FEM. An analogous result is also proved for the streamline diffusion finite element method.
This work was supported by the National Natural Science Foundation of China (10701083 and 10425105), the Chinese National
Basic Research Program (2005CB321704) and the Boole Centre for Research in Informatics at National University of Ireland Cork. 相似文献
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ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献
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