  Superconducting microwave amplifiers are essential for sensitive signal
readout in superconducting quantum processors. Typically based on Josephson
Junctions, these amplifiers require operation at milli-Kelvin temperatures to
achieve quantum-limited performance. Here we demonstrate a quantum microwave
amplifier that employs radiative cooling to operate at elevated temperatures.
This kinetic-inductance-based parametric amplifier, patterned from a single
layer of high-$T_\mathrm{c}$ NbN thin film\cmt{in the form of a nanobridge},
maintains a high gain and meanwhile enables low added noise of 1.3 quanta when
operated at 1.5 Kelvin. Remarkably, this represents only a 0.2 quanta increase
compared to the performance at a base temperature of 0.1 Kelvin. By uplifting
the parametric amplifiers from the mixing chamber without compromising readout
efficiency, this work represents an important step for realizing scalable
microwave quantum technologies.
