70 research outputs found
Orbital hyperfine interaction and qubit dephasing in carbon nanotube quantum dots
Hyperfine interaction (HF) is of key importance for the functionality of
solid-state quantum information processing, as it affects qubit coherence and
enables nuclear-spin quantum memories. In this work, we complete the theory of
the basic hyperfine interaction mechanisms (Fermi contact, dipolar, orbital) in
carbon nanotube quantum dots by providing a theoretical description of the
orbital HF. We find that orbital HF induces an interaction between the nuclear
spins of the nanotube lattice and the valley degree of freedom of the electrons
confined in the quantum dot. We show that the resulting
nuclear-spin--electron-valley interaction (i) is approximately of Ising type,
(ii) is essentially local, in the sense that a radius- and
dot-length-independent atomic interaction strength can be defined, and (iii)
has an atomic interaction strength that is comparable to the combined strength
of Fermi contact and dipolar interactions. We argue that orbital HF provides a
new decoherence mechanism for single-electron valley qubits and spin-valley
qubits in a range of multi-valley materials. We explicitly evaluate the
corresponding inhomogeneous dephasing time for a nanotube-based valley
qubit.Comment: 7 pages, 3 figure
Diszlokáció struktúra -és ikerhatásrok karakterizációja vékony -és multirétegek esetén röntgen vonalprofil analízis alapján
Interpretable neural networks based on continuous-valued logic and multicriteria decision operators
How to implement MCDM tools and continuous logic into neural computation? : Towards better interpretability of neural networks
Dislocation density and Burgers vector population in fiber-textured Ni thin films determined by high-resolution X-ray line profile analysis
Nanocrystalline Ni thin films have been produced by direct current electrodeposition with different additives and current density in order to obtain 〈100〉, 〈111〉 and 〈211〉 major fiber textures. The dislocation density, the Burgers vector population and the coherently scattering domain size distribution are determined by high-resolution X-ray diffraction line profile analysis. The substructure parameters are correlated with the strength of the films by using the combined Taylor and Hall–Petch relations. The convolutional multiple whole profile method is used to obtain the substructure parameters in the different coexisting texture components. A strong variation of the dislocation density is observed as a function of the deposition conditions.</jats:p
Testing goodness-of-fit of random graph models
Random graphs are matrices with independent 0, 1 elements with probabilities
determined by a small number of parameters. One of the oldest model is the
Rasch model where the odds are ratios of positive numbers scaling the rows and
columns. Later Persi Diaconis with his coworkers rediscovered the model for
symmetric matrices and called the model beta. Here we give goodnes-of-fit tests
for the model and extend the model to a version of the block model introduced
by Holland, Laskey, and Leinhard
Nemváltások és nemiszerep-áthágások reprezentációi Az Estben 1910 és 1939 között. In: Replika 85-86 (2014/1-2): 209-225.
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