A superconductor-normal conductor junction device comprises first and second regions (1, 3) of normal material forming first and second junctions with a superconducting material (2), the Fermi level of the first region of normal material being so arranged relative to a given energy level in the superconducting material that charge carriers in the first normal material undergo Andreev reflection at the first junction, resulting in pairs of the charge carriers entering said given energy level in the superconducting material, and the Fermi level of the second region of normal material being so arranged relative to said given level in the superconducting material that said charge carriers conduct from the superconducting material through the second region.
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