to store a digital information. To write the desired state one can apply magnetic field, so that one of the energy minima disappears, so the phase has no choice as to go to the remaining one. To read out an unknown state of the φ junctions one can apply the bias current with value between the two critical currents. If the φ junctions switches to the voltage state, its state was −φ, otherwise, it was +φ. The use of φ junctions as a memory cell (1 bit) was already demonstrated. In quantum domain the φ junction can be used as a two-level system (qubit). See also Josephson effect Josephson energy π Josephson junction Semifluxon Fractional vortices References Superconductivity Josephson effect