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 analogy between the classical wave optics and the quantum wave phenomena

A striking correspondence between the effects of an auxiliary-mode-assisted transfer of light power between two waveguides and an auxiliary-state-assisted transfer of an electron between two quantum dots is highlighted by the example of an exactly solvable model.Comment: To appear in Solid State Communication

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

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

Phonon-induced decoherence of the two-level quantum subsystem due to relaxation and dephasing processes

Phonon-related decoherence effects in a quantum double-well two-level subsystem coupled to a solid are studied theoretically by the example of deformation phonons. Expressions for the reduced density matrix at T=0 are derived beyond the Markovian approximation by means of explicit solution of the non-stationary Schrodinger equation for the interacting electron-phonon system at the initial stage of its evolution. It is shown that as long as the difference between the energies of the electron in the left and the right well greatly exceeds the energy of the electron tunneling between the minima of the double-well potential, decoherence is primarily due to dephasing processes. This case corresponds to a strongly asymmetric potential and spatially separated eigenfunctions localized in the vicinity of one or another potential minimum. In the opposite case of the symmetric potential, the decoherence stems from the relaxation processes, which may be either "resonant" (at relatively long times) or "nonresonant" (at short times), giving rise to qualitatively different temporal evolution of the electron state. The results obtained are discussed in the context of quantum information processing based on the quantum bits encoded in electron charge degrees of freedom.Comment: 20 pages, no 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