Electrical manipulation of an electronic two-state system in Ge/Si quantum dots

We calculate that the electron states of strained self-assembled Ge/Si quantum dots provide a convenient two-state system for electrical control. An electronic state localized at the apex of the quantum dot is nearly degenerate with a state localized at the base of the quantum dot. Small electric fields shift the electronic ground state from apex-localized to base-localized, which permits sensitive tuning of the electronic, optical and magnetic properties of the dot. As one example, we describe how spin-spin coupling between two Ge/Si dots can be controlled very sensitively by shifting the individual dot's electronic ground state between apex and base

Electric-field Manipulation of the Lande' g Tensor of Holes in In0.5Ga0.5As/GaAs Self-assembled Quantum Dots

The effect of an electric field on spin precession in In0.5Ga0.5As/GaAs self-assembled quantum dots is calculated using multiband real-space envelope-function theory. The dependence of the Lande' g tensor on electric fields should permit high-frequency g tensor modulation resonance, as well as direct, nonresonant electric-field control of the hole spin. Subharmonic resonances have also been found in g tensor modulation resonance of the holes, due to the strong quadratic dependence of components of the hole g tensor on the electric field.Comment: 4 pages, 2 figure

Substitutional nickel impurities in diamond: decoherence-free subspaces for quantum information processing

The electronic and magnetic properties of a neutral substitutional nickel (Ni$_s^0$) impurity in diamond are studied using density functional theory in the generalized gradient approximation. The spin-one ground state consists of two electrons with parallel spins, one located on the nickel ion in the $3d^9$ configuration and the other distributed among the nearest-neighbor carbons. The exchange interaction between these spins is due to $p-d$ hybridization and is controllable with compressive hydrostatic or uniaxial strain, and for sufficient strain the antiparallel spin configuration becomes the ground state. Hence, the Ni impurity forms a controllable two-electron exchange-coupled system that should be a robust qubit for solid-state quantum information processing

Anomalous quantum confined Stark effects in stacked InAs/GaAs self-assembled quantum dots

Vertically stacked and coupled InAs/GaAs self-assembled quantum dots (SADs) are predicted to exhibit a strong non-parabolic dependence of the interband transition energy on the electric field, which is not encountered in single SAD structures nor in other types of quantum structures. Our study based on an eight-band strain-dependent ${\bf k}\cdot{\bf p}$ Hamiltonian indicates that this anomalous quantum confined Stark effect is caused by the three-dimensional strain field distribution which influences drastically the hole states in the stacked SAD structures.Comment: 4 pages, 4 figure

Chronology and function of a new circular mammoth bone structure from Kostenki 11

This is the author accepted manuscript. The final version is available from Cambridge University Press via the DOI in this record.We report on assemblages of charcoal, burnt bone and microlithic debitage retrieved by flotation from a new circular mammoth bone feature discovered at Kostenki 11-Ia, Russian Federation, the first time a mammoth bone circle has ever been systematically sampled in this way. New radiocarbon dates are used to provide the first coherent chronology for the site, revealing it as one of the oldest such features on the Russian Plain and confirming occupation of this region during Greenland Stadial 3 at the onset of the last glacial maximum. Implications for human activity within and around the mammoth bone feature are discussed.Leverhulme Trus

Electronic structure of strained InP/GaInP quantum dots

We calculate the electronic structure of nm scale InP islands embedded in $Ga_{0.51}In_{0.49}P$. The calculations are done in the envelope approximation and include the effects of strain, piezoelectric polarization, and mixing among 6 valence bands. The electrons are confined within the entire island, while the holes are confined to strain induced pockets. One pocket forms a ring at the bottom of the island near the substrate interface, while the other is above the island in the GaInP. The two sets of hole states are decoupled. Polarization dependent dipole matrix elements are calculated for both types of hole states.Comment: Typographical error corrected in strain Hamiltonia

System Engineering of Photonic Systems for Space Applications

No abstract availabl