A high sensitivity ultra-low temperature RF conductance and noise measurement setup

TL;DR

This paper presents a highly sensitive RF measurement setup capable of detecting small current fluctuations and conductance at milliKelvin temperatures, enabling detailed analysis of mesoscopic systems and single-electron sources.

Contribution

The authors develop and demonstrate a novel RF noise measurement scheme combining interferometric amplification and impedance transformation for ultra-low temperature applications.

Findings

Achieved noise spectral density measurement GHz bandwidth below amplifier noise floor.

Successfully characterized a subnanosecond single-electron source.

Setup's sensitivity and bandwidth are suitable for manipulating single charges at GHz frequencies.

Abstract

We report on the realization of a high sensitivity RF noise measurement scheme to study small current fluctuations of mesoscopic systems at milliKelvin temperatures. The setup relies on the combination of an interferometric ampli- fication scheme and a quarter-wave impedance transformer, allowing the mea- surement of noise power spectral densities with GHz bandwith up to five orders of magnitude below the amplifier noise floor. We simultaneously measure the high frequency conductance of the sample by derivating a portion of the signal to a microwave homodyne detection. We describe the principle of the setup, as well as its implementation and calibration. Finally, we show that our setup allows to fully characterize a subnanosecond on-demand single electron source. More generally, its sensitivity and bandwith make it suitable for applications manipulating single charges at GHz frequencies.