Wideband Squeezing in a Low-Q Josephson Parametric Amplifier

Josephson parametric amplifiers (JPAs) provide high gain and near–quantum-limited noise performance but typically operate over narrow bandwidths. We present a SQUID-based JPA integrated with a superconducting transmission-line impedance transformer that lowers the resonator Q and broadens the amplifier bandwidth. Operating in the three-wave mixing regime, the device achieves over 16 dB of average gain across a 1 GHz bandwidth. The reduced Q enables single-mode quadrature squeezing with a lower bound of 4 dB over a 360 MHz bandwidth at a fixed flux bias by tuning the pump frequency and power. We also observe two-mode squeezing in the joint quadrature with a lower bound of 3 dB and a maximum of 6 dB for a 1.8 GHz signal–idler separation. These results demonstrate broadband, phase-sensitive amplification beyond the standard quantum limit in a compact, impedance-engineered JPA, showing its potential as a wideband source of squeezed microwave radiation comparable to traveling-wave parametric amplifiers.