Qubit Measurement by Multi-Channel Driving*

We theoretically propose and experimentally implement a method to measure a qubit by driving it close to the frequency of a dispersively coupled bosonic mode. The separation of the bosonic states corresponding to different qubit states begins essentially immediately at maximum rate, leading to a speedup in the measurement protocol. Also the bosonic mode can be simultaneously driven to optimize measurement speed and fidelity.
We experimentally test this measurement protocol using a superconducting qubit coupled to a resonator mode. Compared to the conventional dispersive readout, we observe that our protocol yields higher fidelity for a given integration time. Finally, we use an additional resonator drive to leave the resonator state in vacuum if qubit is in the excited state before the measurement protocol. This suggests that the proposed technique may become useful in unconditionally resetting the resonator to a vacuum state after the measurement pulse.