High-Gain Traveling-Wave Parametric Amplifier Based on Three-Wave Mixing

We extend the theory for a Josephson junction travelling wave parametric amplifier (TWPA) operating in three-wave mixing regime and we propose scheme achieving high gain. The continuous three-mode model [P. K. Tien, J. Appl. Phys. 29, 1347 (1958)] is on one hand extended to describe discrete chain of junctions at frequencies close spectral cutoff where there no up-conversion. On other hand, also develop multimode low-frequency region frequency dispersion linear. find that both cases gain significantly reduced compared prediction by as result increasingly strong generation up-converted modes low frequencies. developed quantitative agreement with experimental observations. To recover gain, engineer dispersive features form two-band spectrum place pump within upper band cutoff. prove exists sweet spot, signal are phase matched, while up-conversion inhibited. This results which grows exponentially length TWPA.