57 Ultra High-Speed Microbridge Chaos Domain

We solve the tetrode microbridge dynamic system problem and its variational equations to determine the largest Lyapunov exponent. We have characterized the dynamic behavior of Josephson tetrode, which consists of five weak-link Josephson junctions for different values of one of the control parameters. We determined the region of control space where noisy oscillation at frequencies of hundreds of gigahertz occurs. Other regions show periodic oscillations. Stewart-McCumber resistive shunt model for NbN electrodes is used in the numerical analysis. We calculate the largest Lyapunov exponent through Gram-Schmitt reorthonormalization algorithm using the dynamics of electrical voltages across the junctions when one of the normal resistances is varied. Result confirms the existence of chaotic oscillation in microbridge device in specified control parameter range.