Characterizing cryogenic amplifiers with a matched temperature-variable noise source

Slawomir Simbierowicz; Visa Vesterinen; Joshua Milem; Aleksi Lintunen; Mika Oksanen; Leif Roschier; Leif Grönberg; Juha Hassel; David Gunnarsson; Russell E Lake

doi:10.1063/5.0028951

Characterizing cryogenic amplifiers with a matched temperature-variable noise source

Rev Sci Instrum. 2021 Mar 1;92(3):034708. doi: 10.1063/5.0028951.

Affiliations

¹ Bluefors Oy, Arinatie 10, 00370 Helsinki, Finland.
² VTT Technical Research Centre of Finland Ltd., QTF Center of Excellence, P.O. Box 1000, FI-02044 VTT, Finland.

PMID: 33820089
DOI: 10.1063/5.0028951

Abstract

We present a cryogenic microwave noise source with a characteristic impedance of 50 Ω, which can be installed in a coaxial line of a cryostat. The bath temperature of the noise source is continuously variable between 0.1 K and 5 K without causing significant back-action heating on the sample space. As a proof-of-concept experiment, we perform Y-factor measurements of an amplifier cascade that includes a traveling wave parametric amplifier and a commercial high electron mobility transistor amplifier. We observe system noise temperatures as low as 680_-200 ⁺²⁰ mK at 5.7 GHz corresponding to 1.5_-0.7 ^+0.1 excess photons. The system we present has immediate applications in the validation of solid-state qubit readout lines.