All-Microwave Control and Dispersive Readout of Gate-Defined Quantum Dot Qubits in Circuit Quantum Electrodynamics

Understand

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.