  A quantum-limited amplifier enables the amplification of weak signals while
introducing minimal noise dictated by the principles of quantum mechanics.
These amplifiers serve a broad spectrum of applications in quantum computing,
including fast and accurate readout of superconducting qubits and spins, as
well as various uses in quantum sensing and metrology. Parametric
amplification, primarily developed using Josephson junctions, has evolved into
the leading technology for highly effective microwave measurements within
quantum circuits. Despite their significant contributions, these amplifiers
face fundamental limitations, such as their inability to handle high powers,
sensitivity to parasitic magnetic fields, and particularly their limitation to
operate only at millikelvin temperatures. To tackle these challenges, here we
experimentally develop a novel quantum-limited amplifier based on
superconducting kinetic inductance and present an extensive theoretical model
to describe this nonlinear coupled-mode system. Our device surpasses the
conventional constraints associated with Josephson junction amplifiers by
operating at much higher temperatures up to 4.5 K. With two distinct spectral
modes and tunability through bias current, this amplifier can operate
selectively in both single and double-mode amplification regimes near the
quantum noise limit. Utilizing a nonlinear thin film exhibiting kinetic
inductance, our device attains gain exceeding 50 dB in a single-mode and 32 dB
in a double-mode configuration while adding 0.35 input-referred quanta of
noise. Importantly, this amplifier eliminates the need for Josephson junctions,
resulting in significantly higher power handling capabilities than
Josephson-based amplifiers. It also demonstrates resilience in the presence of
magnetic fields, offers a straightforward design, and enhances reliability.
