  We theoretically examine the capacitive coupling between two quantum dot
hybrid qubits, each consisting of three electrons in a double quantum dot, as a
function of the energy detuning of the double dot potentials. We show that a
shaped detuning pulse can produce a two-qubit maximally entangling operation in
$\sim$50ns without having to simultaneously change tunnel couplings.
Simulations of the entangling operation in the presence of experimentally
realistic charge noise yield two-qubit fidelities over 90%.
