A singlet - triplet T$_{+}$ based qubit

We theoretically show that the electronic two-spin states singlet and triplet T$_{+}$ are promising candidates for the implementation of a \emph{qubit} in GaAs double quantum dots (DQD). A coherent superposition of the two-spin states is obtained by finite time Landau-Zener-St\"uckelberg interferometry [1] and the single qubit rotations are performed by means of an external magnetic field with a typical amplitude of about $100$ mT. In such a system, the coherent manipulation of the qubit takes place in a time scale of about $1$ ns. We also study the nuclear induced decoherence, mainly due to hyperfine contact coupling between the electronic and nuclear spins, and compute the decoherence time $T_2^{*} \sim10$ ns. \\[4pt] [1] H. Ribeiro and G. Burkard, Phys. Rev. Lett. \textbf{102}, 216802 (2009)