Determining the state of a qubit on a timescale much shorter than its relaxation time is an essential requirement for quantum information processing. With the aid of a new type of non-degenerate parametric amplifier, we demonstrate the continuous detection of quantum jumps of a transmon qubit with 90% fidelity in state discrimination. Entirely fabricated with standard two-step optical lithography techniques, this type of parametric amplifier consists of a dispersion engineered Josephson junction (JJ) array. By using long arrays, containing 103 JJs, we can obtain amplification at multiple eigenmodes with frequencies below 10GHz, which is the typical range for qubit readout. Moreover, by introducing a moderate flux tunability of each mode, employing superconducting quantum interference device (SQUID) junctions, a single amplifier device could potentially cover the entire frequency band between 1 and 10GHz.
@article{arxiv.1909.08037,
title = {Non-degenerate parametric amplifiers based on dispersion engineered Josephson junction arrays},
author = {Patrick Winkel and Ivan Takmakov and Dennis Rieger and Luca Planat and Wiebke Hasch-Guichard and Lukas Grünhaupt and Nataliya Maleeva and Farshad Foroughi and Fabio Henriques and Kiril Borisov and Julian Ferrero and Alexey V. Ustinov and Wolfgang Wernsdorfer and Nicolas Roch and Ioan M. Pop},
journal= {arXiv preprint arXiv:1909.08037},
year = {2023}
}
Comments
P.W. and I.T. contributed equally. 9 pages, 5 figures and appendices