Josephson junction transmission lines as tunable artificial crystals

TL;DR

This paper explores how one-dimensional Josephson junction arrays can be engineered as artificial crystals with tunable microwave band gaps, enabling control over electromagnetic properties for quantum circuits.

Contribution

It introduces a circuit-based approach to design Josephson junction arrays with engineered and tunable microwave band gaps, analogous to electronic band gaps in crystals.

Findings

The band gap depends on array parameters in the linear regime.

Designs can bring the gap below the single junction plasma frequency.

The band gap can be tuned over a wide frequency range with external flux.

Abstract

We investigate one-dimensional Josephson junction arrays with generalized unit cells as a circuit approach to engineer microwave band gaps. An array described by a lattice with a basis can be designed to have a gap in the electromagnetic spectrum, in full analogy to electronic band gaps in diatomic or many-atomic crystals. We derive the dependence of this gap on the array parameters in the linear regime, and suggest experimentally feasible designs to bring the gap below the single junction plasma frequency. The gap can be tuned in a wide frequency range by applying external flux, and it persists in the presence of small imperfections.