Theoretical investigation of JTWPAs containing several junctions per unit cell

In this work we introduce an alternative theoretical method to model Josephson traveling-wave parametric amplifiers. Our theoretical framework relies on applying the variational principle to minimize the action of the system; with it we can take into account the interaction between displaced fields and their effects on the effective nonlinear wave-mixing process. Therefore, our approach allows us to study devices with several junctions within the same unit cell, which might be heterogeneously spaced. In this presentation, we will show that our method converges to conventional approaches when junctions are uniformly spaced, and that certain non-uniform configurations can improve the device's maximum gain and bandwidth.