Resonant-pulse operations on the buried donor charge qubits in semiconductors

A new scheme is proposed for rotations of a double-donor charge qubit whose logical states are defined by the two lowest energy states of a single electron localized around one or another donor. It is shown that making use of the microwave pulses tuned to the resonance with an auxiliary excited molecular level allows for implementation of various one-qubit operations in very short times. Decoherence effects are analyzed by the example of the P$_2^+$:Si system and shown to be weak enough for experimental realization of this scheme being possible.Comment: 4 pages, 1 figure, to appear in PR

Localized electron state in a T-shaped confinement potential

We consider a simple model of an electron moving in a T-shaped confinement potential. This model allows for an analytical solution that explicitly demonstrates the existence of laterally bound electron states in quantum wires obtained by the cleaved edge overgrowth technique.Comment: 6 pages, 5 figure

On the Thermal Stability of Graphone

Molecular dynamics simulation is used to study thermally activated migration of hydrogen atoms in graphone, a magnetic semiconductor formed of a graphene monolayer with one side covered with hydrogen so that hydrogen atoms are adsorbed on each other carbon atom only. The temperature dependence of the characteristic time of disordering of graphone via hopping of hydrogen atoms to neighboring carbon atoms is established directly. The activation energy of this process is found to be Ea=(0.05+-0.01) eV. The small value of Ea points to extremely low thermal stability of graphone, this being a serious handicap for practical use of the material in nanoelectronics.Comment: 3 figure

Selective electron transfer between the quantum dots under the resonant pulse

The coherent quantum dynamics of an electron in the quantum-dot ring structure under the resonant electromagnetic pulse is studied theoretically. A possibility of the selective electron transfer between any two dots is demonstrated. The transfer probability as a function of the pulse and dot parameters is calculated. It is shown that this probability can be close to unity. The factors lowering the transfer probability in real systems are discussed. The results obtained may be used in the engineering of novel nanoelectronic devices for quantum bits processing.Comment: Presented at the International Symposium "Quantum Informatics - 2004", Moscow, October 5-8, 2004; to appear in Fiz. Tekh. Poluprovodn. (St. Petersburg

Comment on "Influence of Pair Breaking and Phase Fluctuations on Disordered High Tc Cuprate Superconductors"

It is shown that an account for combined effect of both nonmagnetic and magnetic scatterers on Tc and/or an assumption about a non-pure d-wave order parameter allows for a quantitative explanation of the experimental data on the electron irradiation-induced suppression of superconductivity in Y-123 single crystals within the AG-like pair breaking theory, without resorting to phase fluctuations effects.Comment: Comment on the paper by F. Rullier-Albenque et al., Phys. Rev. Lett. 91, 047001 (2003