Coupler-mediated unconditional reset of fixed-frequency superconducting qubits

As coherence times of superconducting qubits increase, a method for fast and reliable reset is needed to achieve high repetition rates. Moreover, for mid-circuit readout and error correcting schemes high fidelity active qubit reset is required. Here, we present an unconditional reset protocol for fixed frequency qubits in a flux tunable multi-qubit coupler architecture. Our reset protocol is based on a single parametric flux pulse, transferring the qubit excitation coherently to a cold and rapidly decaying transmission-line resonator, which is directly coupled to a 50 Ω environment. After the reset pulse with a typical duration of 400 ns the remaining excited state population is reduced to 0.5%, decreasing the effective qubit temperature from ≈50 mK to ≈35 mK. This multi-qubit coupler based reset method may be extended to realize the simultaneous reset of multiple qubits using a single parametric flux pulse.