  Achieving fast and precise initialization of qubits is a critical requirement
for the successful operation of quantum computers. The combination of
engineered environments with all-microwave techniques has recently emerged as a
promising approach for the reset of superconducting quantum devices. In this
work, we experimentally demonstrate the utilization of a single-junction
quantum-circuit refrigerator (QCR) for an expeditious removal of several
excitations from a transmon qubit. The QCR is indirectly coupled to the
transmon through a resonator in the dispersive regime, constituting a carefully
engineered environmental spectrum for the transmon. Using single-shot readout,
we observe excitation stabilization times down to roughly $500$ ns, a $20$-fold
speedup with QCR and a simultaneous two-tone drive addressing the $e$-$f$ and
$f0$-$g1$ transitions of the system. Our results are obtained at a $48$-mK
fridge temperature and without postselection, fully capturing the advantage of
the protocol for the short-time dynamics and the drive-induced detrimental
asymptotic behavior in the presence of relatively hot other baths of the
transmon. We validate our results with a detailed Liouvillian model truncated
up to the three-excitation subspace, from which we estimate the performance of
the protocol in optimized scenarios, such as cold transmon baths and fine-tuned
driving frequencies. These results pave the way for optimized reset of
quantum-electric devices using engineered environments and for
dissipation-engineered state preparation.
