Dynamic stabilization of a microwave-driven Josephson tunnel junction against a period-doubling bifurcation

The authors present theoretical and experimental results on the effect of periodic perturbations on microwave-driven Josephson tunnel junctions close to a period-doubling bifurcation. The theory, which is quite general, describes how a periodic near-resonant perturbation changes the stability of the system. The phenomenon was investigated experimentally in small Nb-NbO_x-Pb tunnel junctions, and experimental findings were found to be in agreement with the theory. The effect has importance for the performance of parametric amplifiers based on Josephson tunnel junctions