In situ calibration of microwave attenuation and gain using a cryogenic on-chip attenuator

We demonstrate gain and added-noise calibration of cryogenic microwave amplification chains, using an on-chip, heatable attenuator. By comparing DC and RF heating and analyzing the resulting thermal noise power spectral density, the amplification chain itself provides an absolute power reference, eliminating the need for a calibrated noise source. Our heatable attenuator dissipates only ~1 nW of power and reaches steady state within milliseconds. This approach enables fast, broadband characterization of near-quantum-limited parametric amplifiers used in superconducting quantum processors and related systems.