Switching effect in squids coupled by Josephson junction

In this paper, a switching characterization of a system consisting of two superconducting quantum interference devices (SQUIDs) coupled by a Josephson junction (JJ) is presented. We argue that the hysteretic switching between distinguishable states of SQUIDs can be used as an ultrasensitive microwave detector. In summary, quantitative characterization of coupled 2 SQUID system was presented. Three out of four states of the system were observed and discussed. Switching from higher energy to lower energy states was investigated by pulsed measurements. Presented device could be used as a sensitive detector by measuring its state occupancy by methods shown above, while superconducting cavity is excited by microwaves. Amplitude of current generated by a single microwave photon in the cavity with frequency in GHz range, seems to be sufficient to induce switching of a state of one of the coupling JJs in SQUIDs. (authors)