  The ability to fast reset a qubit state is crucial for quantum information
processing. However, to actively reset a qubit requires engineering a pathway
to interact with a dissipative bath, which often comes with the cost of reduced
qubit protection from the environment. Here, we present a novel multi-purpose
architecture that enables fast reset and protection of superconducting qubits
during control and readout. In our design, two on-chip diplexers are connected
by two transmission lines. The high-pass branch provides a flat passband for
convenient allocation of readout resonators above the qubit frequencies, which
is preferred for reducing measurement-induced state transitions. In the
low-pass branch, we leverage a standing-wave mode below the maximum qubit
frequency for a rapid reset. The qubits are located in the common stopband to
inhibit dissipation during coherent operations. We demonstrate resetting a
transmon qubit from its first excited state to the ground state in 100 ns,
achieving a residual population of 2.7%, mostly limited by the thermal effect.
The reset time may be further shortened to 27 ns by exploiting the coherent
population inversion effect. We further extend the technique to resetting the
qubit from its second excited state. Our approach promises scalable
implementation of fast reset and qubit protection during control and readout,
adding to the toolbox of dissipation engineering.
