Wave packet transmission of Bloch electron manipulated by magnetic field

We study the phenomenon of wave packet revivals of Bloch electrons and explore how to control them by a magnetic field for quantum information transfer. It is showed that the single electron system can be modulated into a linear dispersion regime by the "quantized" flux and then an electronic wave packet with the components localized in this regime can be transferred without spreading. This feature can be utilized to perform the high-fidelity transfer of quantum information encoded in the polarization of the spin. Beyond the linear approximation, the re-localization and self-interference occur as the novel phenomena of quantum coherence.Comment: 6 pages, 5 figures, new content adde

Quantum state swapping via qubit network with Hubbard interaction

We study the quantum state transfer (QST) in a class of qubit network with on-site interaction, which is described by the generalized Hubbard model with engineered couplings. It is proved that the system of two electrons with opposite spins in this quantum network of $N$ sites can be rigorously reduced into $N$ one dimensional engineered single Bloch electron models with central potential barrier. With this observation we find that such system can perform a perfect QST, the quantum swapping between two distant electrons with opposite spins. Numerical results show such QST and the resonant-tunnelling for the optimal on-site interaction strengths.Comment: 4 pages, 3 figure

THEORETICAL STUDIES OF BILIPROTEIN CHROMOPHORES AND RELATED BILE PIGMENTS BY MOLECULAR ORBITAL AND RAMACHANDRAN TYPE CALCULATIONS

Ramachandran calculations have been used to gain insight into steric hindrance in bile pigments related to biliprotein chromophores. The high optical activity of denatured phycocyanin, as compared to phycoerythrin, has been related to the asymmetric substitution at ring A, which shifts the equilibrium towards the P-helical form of the chromophore. Geometric effects on the electronic structures and transitions have then been studied by molecular orbital calculations for several conjugation systems including the chromophores of phycocyanin. phytochrome P,, cations, cation radicals and tautomeric forms. For these different chromophores some general trends can be deduced. For instance, for a given change in the gross shape (e.g. either unfolding of the molecule from a cyclic-helical to a fully extended geometry, or upon out-of-plane twists of the pyrrole ring A) of the molecules under study, the predicted absorption spectra all change in a simikar way. Nonetheless, there are characteristic distinctions between the different n-systems, both in the transition energies and the charge distribution, which can be related to their known differences in spectroscopic properties and their reactivity