  Quantum-limited Josephson parametric amplifiers play a pivotal role in
advancing the field of circuit quantum electrodynamics by enabling the fast and
high-fidelity measurement of weak microwave signals. Therefore, it is necessary
to develop robust parametric amplifiers with low noise, broad bandwidth, and
reduced design complexity for microwave detection. However, current broadband
parametric amplifiers either have degraded noise performance or rely on complex
designs. Here, we present a device based on the broadband impedance-transformed
Josephson parametric amplifier (IMPA) that integrates a horn-like coplanar
waveguide (CPW) transmission line, which significantly decreases the design and
fabrication complexity, while keeping comparable performance. The device shows
an instantaneous bandwidth of 700(200) MHz for 15(20) dB gain with an average
saturation power of -110 dBm and near quantum-limited added noise. The
operating frequency can be tuned over 1.4 GHz using an external flux bias. We
further demonstrate the negligible back-action from our device on a transmon
qubit. The amplification performance and simplicity of our device promise its
wide adaptation in quantum metrology, quantum communication, and quantum
information processing.
