The aim of this work package is to improve the sensitivity and readout of quantum sensors with the help of JTWPA devices to quantum levels with minimum backaction. This will be accomplished through integration of the JTWPA with different types of quantum sensors. The research activity will include optimisation of circuit design parameters and physical layout of the amplifier and quantum sensors, optimisation of the fabrication process and the preparation of functional samples based on the outputs of WP1, WP2 and WP3.

The final goal is to integrate JTWPA with nanoSQUID sensors operating in a dispersive mode and rf single- charge detectors (transistors) operating either on single electrons or single Cooper pairs and optimised for error counting in single electron pumps, and to demonstrate frequency multiplexing in these circuits, and flux and charge sensitivities approaching the standard quantum limit. Both selected sensors, the nanoSQUID and the single-charge transistor in the superconducting state (Cooper-pair transistor) can be regarded as macroscopic quantum systems as their behaviour is governed by a macroscopically large number of Cooper pairs.