Josephson junction mixing

It is shown that a Josephson junction, biased at a voltage V0 and driven simultaneously by two monochromatic sources at the frequencies ω1 and ω2, produces an output power at the frequency ω3 = ω1 — nω2 and that this frequency is independent of the Josephson frequency ω0 = 2eV0/ℏ. The power output depends upon the dc bias, showing fine structure with a voltage periodicity of ℏω2/2e.