We demonstrated coherent control of a quantum two-level system based on two-electron spin states in a double quantum dot, allowing state preparation, coherent manipulation, and projective readout. These techniques are based on rapid electrical control of the exchange interaction. Separating and later recombining a singlet spin state provided a measurement of the spin dephasing time, T2*, of app...

We review our recent work addressing various theoretical issues in spin-based quantum dot quantum computation and quantum information processing. In particular, we summarize our calculation of electron exchange interaction in two-electron double quantum dots and multi-electron double dots, and discuss the physical implication of our results. We also discuss possible errors and how they can be c...

The effect of the exchange-correlation potential in ab initio electron transport calculations is investigated by constructing optimized effective potentials using different energy functionals or the electron density from second-order perturbation theory. The authors calculate electron transmission through two atomic chain systems, one with charge transfer and one without. Dramatic effects are c...

Electron spin dynamics are studied in Ga-doped ZnO single crystals by time-resolved Faraday and Kerr rotation spectroscopies. Long-lived coherence with two dephasing processes is discovered where the characteristic time up to 5.2 ns at room temperature. Through dependence measurements of laser wavelength temperature, room-temperature long-lived signal attributed localized electrons. The (relaxa...

The influence of hypothetical new interactions beyond the Standard Model on atomic spectra has attracted recent interest. In present work, interelectronic photon-exchange corrections and radiative quantum electrodynamic to contribution energy levels few-electron ions from a interaction are calculated. $1s$, $2s$ $2p_{1/2}$ ground states H-like, Li-like B-like considered, as motivated by proposa...

We present a review of our recent results for the comparative evaluation of the induced exchange interaction and quantum noise mediated by the bosonic environment in two-qubit systems. We report new calculations for P-donor-electron spins in Si-Ge type materials. Challenges and open problems are discussed.