  High-fidelity quantum non-demolition qubit measurement is critical to error
correction and rapid qubit feedback in large-scale quantum computing.
High-fidelity readout requires passing a short and strong pulse through the
qubit's readout resonator, which is then processed by a sufficiently high
bandwidth, high saturation power, and quantum-limited amplifier. We have
developed a design pipeline that combines time-domain simulation of the
un-truncated device Hamiltonian, fabrication constraints, and maximization of
saturation power. We have realized an amplifier based on a modified NIST
tri-layer Nb fabrication suite which utilizes an array of 25 radio frequency
Superconducting QUantum Interference Devices (rf SQUIDs) embedded within a
low-Q resonator powered by a high-power voltage pump delivered via a diplexer
on the signal port. We show that, despite the intensity of the pump, the device
is quantum-efficient and capable of high-fidelity measurement limited by state
transitions in the transmon. We present experimental data demonstrating up to
-91.2 dBm input saturation power with 20 dB gain, up to 28 MHz instantaneous
bandwidth, and phase-preserving qubit measurements with 62% quantum efficiency.
