  A quantum dot hybrid qubit formed from three electrons in a double quantum
dot has the potential for great speed, due to presence of level crossings where
the qubit becomes charge-like. Here, we show how to take full advantage of the
level crossings in a pulsed gating scheme, which decomposes the spin qubit into
a series of charge transitions. We develop one and two-qubit dc quantum gates
that are simpler than the previously proposed ac gates. We obtain closed form
solutions for the control sequences and show that these sub-nanosecond gates
can achieve high fidelities.
