Pulsed Reset Protocol for Fixed-Frequency Superconducting Qubits

Increasing coherence times of quantum bits is a fundamental challenge in the field of quantum computing. With long-lived qubits it is, however, inefficient to wait until the qubits have relaxed to their ground state after completion of an experiment. Moreover, for error-correction schemes it is important to rapidly reinitialize syndrome qubits. We present a simple pulsed qubit reset protocol based on a two-pulse sequence. A first pulse transfers the excited-state population to a higher excited qubit state and a second pulse transfer it into a lossy environment provided by a low-Q transmission-line resonator, which is also used for qubit read-out. We show that the remaining excited-state population can be suppressed to (1.7±0.1)% and that this figure may be reduced by further improving the pulse calibration.