Sub-GHz Josephson parametric amplifiers for the readout of sensors and quantum dots*

We present our latest experimental results on sub-GHz Josephson parametric amplifiers (JPAs) fabricated with our Nb/Al-AlO_x/Nb junction process [1]. The early generation of our flux-driven reflection-type JPA has found applications in the radio-frequency readout of bolometers [2], as well as quantum dots [3]. We have recently addressed bandwidth limitations by engineering a partially reconfigurable impedance transformer. With a bandwidth of 10 MHz at 20 dB gain at 600 MHz, the improved JPA is in line with the requirements of fast readout schemes for, e.g., semiconductor quantum dots. In addition, we have experimented with a variant where unwanted non-linearities are suppressed by alternating the dipolar orientation of superconducting nonlinear asymmetric inductive elements (SNAILs) in an array.

[1] Leif Grönberg et al., Supercond. Sci. Technol. 30, 125016 (2017)
[2] Roope Kokkoniemi et al., Commun. Phys. 2, 124 (2019)
[3] P. Apostolidis et al., arXiv:2007.03588