Nonlinearity engineering with the Quarton

Abstract

In this thesis, we show the principles and applications of a new technique we call "nonlinearity engineering" using a recent superconducting qubit, the Quarton. In traditional nonlinear optics, nonlinear effects are usually weak perturbations to linear interactions. Similarly, microwave quantum optics with superconducting circuits relies on the Josephson junction for a negative Kerr nonlinearity that is much weaker than its associated linear energy. Recently, a new superconducting qubit known as the "Quarton" can offer non-perturbatively strong nonlinearity. Here, we demonstrate the general principle of using the Quarton's positive Kerr and zero linear energy to perform nonlinearity engineering, i.e. the selective design of the nonlinear properties of microwave artificial atoms, metamaterials, and photons in a manner that (to the best of our knowledge) has no optical analog. We show that for Quarton mediated light-matter coupling, the Quarton can erase or amplify the nonlinearity of artificial atoms and metamaterials. Without nonlinearity, matter behaves light-like and we find (to our best knowledge) the first theoretical demonstration of cross-Kerr between linear microwave photon modes. We extend these fundamental results and provide a practical application by designing a Josephson traveling wave photon detector