Fast and Unconditional All-Microwave Reset of a Superconducting Qubit

Abstract

Active qubit reset is a key operation in many quantum algorithms, and particularly in error correction codes. Here, we experimentally demonstrate a reset scheme of a three level transmon artificial atom coupled to a large bandwidth resonator. The reset protocol uses a microwave-induced interaction between the $|f,0⟩$ and $|g,1⟩$ states of the coupled transmon-resonator system, with $|g⟩$ and $|f⟩$ denoting the ground and second excited states of the transmon, and $|0⟩$ and $|1⟩$ the photon Fock states of the resonator. We characterize the reset process and demonstrate reinitialization of the transmon-resonator system to its ground state with $0.2\%$ residual excitation in less than $500\mathrm{ns}$. Our protocol is of practical interest as it has no requirements on the architecture, beyond those for fast and efficient single-shot readout of the transmon, and does not require feedback.