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arXiv · 1810.05767

Radio-frequency reflectometry of a quantum dot using an ultra-low-noise SQUID amplifier

F. J. Schupp·F. Vigneau·Y. Wen·A. Mavalankar·J. Griffiths·G. A. C. Jones·I. Farrer·D. A. Ritchie·C. G. Smith·L. C. Camenzind·L. Yu·D. M. Zumbühl·G. A. D. Briggs·N. Ares·E. A. Laird
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Abstract

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/\sqrt{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 microsecond of integration time.

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F. J. Schupp, F. Vigneau, Y. Wen, A. Mavalankar, J. Griffiths, G. A. C. Jones, I. Farrer, D. A. Ritchie, C. G. Smith, L. C. Camenzind, L. Yu, D. M. Zumbühl, G. A. D. Briggs, N. Ares, E. A. Laird. 2018-10-13. Radio-frequency reflectometry of a quantum dot using an ultra-low-noise SQUID amplifier. https://doi.org/10.1063/5.0005886

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