Simulations of chaos generation from Josephson junctions with various junction parameters

29th International Symposium on Superconductivity

Hiwatashi, R.^1 ; Tamura, Y.^1 ; Shimakage, H.^1

Graduate School of Science and Engineering, Ibaraki University, Hitachi, Ibaraki

316-8511, Japan^1

关键词: Chaos characteristics;    Frequency margins;    Josephson-junction;    Junction parameters;    Lyapunov exponent;    Random number generators;    Resistance values;    Voltage waveforms;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/871/1/012079/pdf
DOI  :  10.1088/1742-6596/871/1/012079

来源: IOP

【 摘 要 】

It is well known that voltage waveforms between electrodes of Josephson junctions under irradiation of a microwave behave chaos characteristics under appropriate conditions. In order to apply the chaos to a random number generator, we have been studying Josephson chaos by simulations. In the simulation, the Josephson junction is assumed to fabricate with YBCO materials. We used a RCSJ model in order to present an equivalent circuit of the Josephson junction, and derived a derivative equation. Lyapunov exponents, which determined if the state of the Josephson junction was chaotic or not, were calculated from time evolutions of voltages obtained from the equation. In the simulation, junction parameters were assigned feasible values for an actual YBCO Josephson junctions. As a result, we found that chaos can be generated by adjusting element parameters. Moreover, we found that there were lower limits in the resistance values for generation of chaos. In addition, we found that frequency margins, at which the chaos was obtained, were broadened by decrease of the resistance and increase of capacitance.