  Developing fast and accurate control and readout techniques is an important
challenge in quantum information processing with semiconductor qubits. Here, we
study the dynamics and the coherence properties of a GaAs/AlGaAs double quantum
dot (DQD) charge qubit strongly coupled to a high-impedance SQUID array
resonator. We drive qubit transitions with synthesized microwave pulses and
perform qubit readout through the state dependent frequency shift imparted by
the qubit on the dispersively coupled resonator. We perform Rabi oscillation,
Ramsey fringe, energy relaxation and Hahn-echo measurements and find
significantly reduced decoherence rates down to $\gamma_2/2\pi\sim 3\,\rm{MHz}$
corresponding to coherence times of up to $T_2 \sim 50 \, \rm{ns}$ for charge
states in gate defined quantum dot qubits.
