Superconducting microwave resonators with non-centrosymmetric nonlinearity

TL;DR

This paper explores the design and experimental demonstration of superconducting microwave resonators with embedded rf SQUIDs that exhibit non-centrosymmetric nonlinearity, enabling efficient three-wave mixing and parametric effects.

Contribution

It introduces a novel resonator configuration with tunable non-centrosymmetric nonlinearity, demonstrating multiple parametric effects in superconducting microwave circuits.

Findings

Demonstrated second harmonic generation and half tone generation.

Achieved parametric amplification and deamplification.

Showed tunability of nonlinearity via external magnetic field.

Abstract

We investigated both theoretically and experimentally open-ended coplanar waveguide resonators with rf SQUIDs embedded in the central conductor at different positions. These rf SQUIDs can be tuned by an external magnetic field and thus may exhibit the non-centrosymmetric nonlinearity of $\chi^{(2)}$ type with suppressed Kerr nonlinearity. We demonstrated that this nonlinearity allows for efficient mixing of $\lambda/2$ and $\lambda$ modes in the cavity and thus enables various parametric effects with three wave mixing. These effects are the second harmonic generation, the half tone generation, the parametric amplification in both degenerate and non-degenerate regimes and deamplification in degenerate regime.