to $B = 3 \ Oe$.

![\[fig:epsart\] Voltage jumps due to changes of quantum numbers in magnetic field at the bias currents through the structure $I \approx 20 \ nA $ observed at the temperature $T \approx 1.1 \ K $ at measurement of the structures with square side of the loops $a \approx  20 \ \mu m$. A part of magnetic dependence measured from $B = 3 \ Oe$ to $B = -3 \ Oe$ is shown. The voltage jumps up and down with the period $B _{0} \approx 0.053 \ Oe $ and the amplitude of the jumps is modulated with the period $B _{m} \approx 0.8 \ Oe $ in the whole region from $B = 3 \ Oe$ to $B = -3 \ Oe$, see Fig.8 of Supporting Information.](Fig3)

The observation of these jumps has the critical importance for the opportunity to use the DDCI for high sensitive detection of magnetic flux. The conventional theory [@Tink75] and numerous experiments [@PCJETP07; @Tanaka04; @APL2016; @JETP07J; @PCScien07; @PLA2012] testify to the sharpness of the change of the probability $P(n)$ of the $n$ state of superconducting loop with enough big value of the persistent current $I _{p,A}$. The theory predicts 