  The author analyzes quantum computation with the hybrid qubit (HQ) that is
encoded using the three-electron configuration of a double quantum dot. All
gate operations are controlled with electric signals, while the qubit remains
at an optimal operation point that is insensitive to noise. An effective
single-qubit description is derived, and two-qubit interactions are suggested
using Coulomb and exchange interactions. Universal quantum control is described
and numerically simulated using realistic parameters for HQs in Si and GaAs.
High-fidelity quantum computing at the threshold of quantum error correction is
possible if the Coulomb interactions between the HQs stay weak.
