Cryogenic amplification of image-charge detection for readout of quantum states of electrons on liquid helium

Accurate detection of quantum states is a vital step in the development of quantum computing. Image-charge detection of quantum states of electrons on liquid helium can potentially be used for the readout of a single-electron qubit; however, low sensitivity due to added noise hinders its usage in high-fidelity and high-bandwidth (BW) applications. One method to improve the readout accuracy and bandwidth is to use cryogenic amplifications near the signal source to minimize the effects of stray capacitance. We experimentally demonstrate a two-stage amplification scheme with a low power dissipation of 90 mu W at the first stage located at the still plate of the dilution refrigerator and a high gain of 40dB at the second stage located at the 4 K plate. The good impedance matching between different stages and output devices ensures high BW and constant gain in a wide frequency range. The detected image-charge signals are compared for one-stage and two-stage amplification schemes.

Automated summary

Accurate detection of quantum states is crucial for the development of quantum computing. Using cryogenic amplifications near the signal source can improve the readout accuracy and bandwidth of quantum states. Experimental demonstration of a two-stage amplification scheme shows low power dissipation and high gain, ensuring high bandwidth and constant gain in a wide frequency range.