place when the persistent current (1) increases in the loop without the current leads with the change of the magnetic flux $\Phi = BS + LI_{p}$ up to a critical value [@Geim2003; @Moler2007; @Nat2016]. The pair velocity $v = (2\pi \hbar/ml)(n - \Phi /\Phi _{0})$ can increase with the $\Phi $ variation up to the depairing velocity $v _{c} = \hbar /m \surd 3 \xi (T)$ [@Tink75] but cannot exceed this value $|v| \leq v _{c}$. Therefore the quantum number should change at $|n - \Phi /\Phi _{0}| \leq l/2\pi \surd 3 \xi (T)$ [@Geim2003; @Moler2007; @Nat2016]. The magnetic flux at which the quantum number $n$ changes may be not equal $\Phi = (n+0.5)\Phi _{0}$ and may be different in ascending and descending magnetic field.

The jumps of the critical current (6) and the voltage at a non-zero bias current $I \neq 0$ can be observed only if the quantum numbers of the upper loop $n _{u}$ and the lower loop $n _{d}$ change at different $\Phi $ values. The voltage may jump up (when the sum $n _{u} + n _{d}$ becomes an odd number) and down (when the sum $n _{u} + n _{d}$ becomes again an even 