Sensitive radio-frequency read-out of quantum dots using an ultra-low-noise SQUID amplifier

Fault-tolerant spin-based quantum computers will require fast and accurate qubit readout. This can be achieved using radio-frequency reflectometry given sufficient sensitivity to the change in quantum capacitance associated with the qubit states. Here, we demonstrate a 23-fold improvement in capacit...

Full description

Bibliographic Details
Main Authors: Schupp, FJ, Vigneau, F, Wen, Y, Mavalankar, A, Griffiths, J, Jones, GAC, Farrer, I, Ritchie, DA, Smith, CG, Camenzind, LC, Yu, L, Zumbühl, DM, Briggs, GAD, Ares, N, Laird, EA
Format: Journal article
Language:English
Published: AIP Publishing 2020
Description
Summary:Fault-tolerant spin-based quantum computers will require fast and accurate qubit readout. This can be achieved using radio-frequency reflectometry given sufficient sensitivity to the change in quantum capacitance associated with the qubit states. Here, we demonstrate a 23-fold improvement in capacitance sensitivity by supplementing a cryogenic semiconductor amplifier with a SQUID preamplifier. The SQUID amplifier operates at a frequency near 200 MHz and achieves a noise temperature below 600 mK when integrated into a reflectometry circuit, which is within a factor 120 of the quantum limit. It enables a record sensitivity to capacitance of 0.07 aF/√Hz. The setup is used to acquire charge stability diagrams of a gate-defined double quantum dot in a short time with a signal-to-noise ration of about 38 in 1 µs of integration time.