Cryogenic amplifier for shot noise measurement at 20 mK

Abstract

We developed a shot noise measurement system for mesoscopic conductors (typical resistance h/2e2 = 12.9 kΩ) at very low temperature (∼20 mK). To realize required high-resolution measurement, we made a high-electron-mobility-transistor (HEMT)-based cryogenic amplifier working at a target frequency range (∼2.5 MHz), whose gain flatness and input voltage noise were carefully tuned. We can suppress the 1/f noise of the amplifier by using two HEMTs in parallel. The performance of the noise measurement system at 20 mK was demonstrated for a quantum point contact with high experimental accuracy below 10−29 A2/Hz.