Wide-band capacitance measurement on a semiconductor double quantum dot for studying tunneling dynamics

We propose and demonstrate wide-band capacitance measurements on a semiconductor double quantum dot (DQD) to study tunneling dynamics. By applying phase-tunable high-frequency signals independently to the DQD and a nearby quantum-point-contact charge detector, we successfully measure current proportional to the capacitance associated with the single-electron motion over a wide frequency range from Hz to a few tens of GHz. Analyzing the phase and the frequency dependence of the signal allows us to extract the characteristic tunneling rates. We show that, by applying this technique to the interdot tunnel coupling regime, quantum capacitance reflecting the strength of the quantum-mechanical coupling can be measured.