I. Introduction
A josephson junction (JJ) [1], being a superconducting device, is a natural candidate to detect elusive, weak signals [2], [3], inasmuch it can be cooled as much as necessary to tame thermal noise that might cover the signal. Needless to say, high-quality detection is fundamental in many diverse fields, from gigahertz astronomy and axions search [4], [5], [6], [7], to quantum computing [8], [9], [10] and superconducting electronics [11], [12].