_{0} $ (or $\Phi \approx (n+0.5) \Phi _{0} $). One may expect to increase the flux sensitivities in $\epsilon /2$ times if the jump $V_{max} - V _{min}$ is not less than the voltage variation of the conventional dc SQUID.

In order to ensure that the change of the quantum number $n _{u}$ results to the voltage jump and to measure its value we used a real structures shown on Fig.2. The structure was fabricated by e-beam lithography to form suspended resist mask and double angle shadow evaporation of aluminum ($d \approx 30 \ nm$ and $d \approx 35 \ nm$) with intermediate first aluminum layer oxidation. This technology allows to make two independent superconducting square contours weakly connected by two Josephson junctions in the two points $J _{a}$ and $J _{b}$, Fig. 1. The contours are shifted relative to one another and there are two extra Josephson junctions $J _{t1}$ and $J _{t2}$ because of this technology. The structures with square side of the loops $a \approx  4 \ \mu m$ and $a \approx  20 \ \mu m$ were made and investigated. The width of the loops was $w \approx 400 \ nm$ and their cross section $s = 