Realization of a single-Cooper-pair Josephson laser

Abstract

The authors couple a microwave cavity to a voltage-biased Cooper-pair transistor, which emits photons at the Josephson frequency $\frac{2e\phantom{\rule{0}{0ex}}V}{\mathrm{\ensuremath{\Elzxh}}}$. If that frequency matches the cavity frequency, photons build up in it, which in turn creates back-action on the Cooper-pair transistor leading to stimulated rather than spontaneous tunneling.