Rapid unconditional active reset of frequency-tunable superconducting qubits via a metamaterial waveguide Purcell filter*

Rapid and deterministic reset of qubits to known pure states is one of the most crucial enablers for quantum information processing. In particular, recent advances in unconditional active reset schemes have led to improvements in various tasks such as quantum error correction and resource state preparation, as their speed and fidelity are not constrained by the quality of readout.

 

We introduce a rapid unconditional active reset scheme for frequency-tunable superconducting qubits by coupling qubits directly to a dispersive bath realized by a metamaterial waveguide Purcell filter. The wide passband of the metamaterial waveguide, in concert with  sharp suppression of the photonic density of states outside of it, enables simultaneous multi-level reset and strong coupling. Through a straightforward parametric flux modulation, we demonstrate the ability to rapidly reset the first three lowest-energy states of a transmon qubit to the ground state, while maintaining a high T₁ lifetime that is not limited by Purcell decay.