Towards a traveling-wave parametric amplifier with two-octave bandwidth

In recent years, traveling-wave parametric amplifiers (TWPAs) have become essential for readout of quantum circuits, providing a gain of 15-20 dB over a bandwidth of more than 1 GHz and with near-quantum-limited noise. While TWPAs are widely used in quantum computing, certain applications in other fields, such as radio astronomy, require similar amplifiers but with larger bandwidths extending from e.g. 4 to 12 GHz. Here we present a TWPA based on an array of ~2400 rf-SQUIDs operating in the three-wave-mixing regime, with a 3-dB bandwidth of 3.6 to 8.3 GHz. Our device delivers a gain of 20 dB and exhibits a saturation power of approximately -90 dBm. Employing this TWPA as the first amplifier in our readout chain, we achieve a total system noise of 2-3 photons across the entire bandwidth. Finally, we discuss how to extend the bandwidth towards two octaves and how to improve the flatness of the gain profile.