  Achieving fast gates and long coherence times for superconducting qubits
presents challenges, typically requiring either a stronger coupling of the
drive line or an excessively strong microwave signal to the qubit. To address
this, we introduce on-chip filters of the qubit drive exhibiting a stopband at
the qubit frequency, thus enabling long coherence times and strong coupling at
the subharmonic frequency, facilitating fast single-qubit gates, and reduced
thermal load. The filters exhibit an extrinsic relaxation time of a few seconds
while enabling sub-10-ns gates with subharmonic control. Here we show up to
200-fold improvement in the measured relaxation time at the stopband.
Furthermore, we implement subharmonic driving of Rabi oscillations with a $\pi$
pulse duration of 12 ns. Our demonstration of on-chip filters and efficient
subharmonic driving in a two-dimensional quantum processor paves the way for a
scalable qubit architecture with reduced thermal load and noise from the
control line.
