A method for producing a quantum device comprising forming a supraconductive layer, forming a mask on the supraconductive layer, the mask comprising masking patterns and at least two openings alternately in a direction, the at least two openings being separated from one another by a separation distance pi (i=1 . . . n), and further each having a width di (i=1 . . . n+1), such as the separation distance pi and a width di are less than a coherence length of a Cooper pair in said supraconductive material, and modifying, through the at least two openings, of the exposed portions of the supraconductive layer, so as to form at least two barriers of width di separating the supraconductive regions.