Quantum metamaterials: Electromagnetic waves in a Josephson qubit line

TL;DR

This paper explores how a transmission line of superconducting qubits can manipulate electromagnetic waves, creating dynamic photonic structures and controlled wave transport due to quantum coherence effects.

Contribution

It introduces novel effects like a breathing photonic crystal and a quantum Archimedean screw driven by the quantum states of superconducting qubits.

Findings

Demonstrates a photonic crystal with oscillating bandgap.

Shows controlled transport of Josephson plasma waves.

Highlights quantum coherence as a tool for electromagnetic control.

Abstract

We consider the propagation of a classical electromagnetic wave through a transmission line, formed by identical superconducting charge qubits inside a superconducting resonator. Since the qubits can be in a coherent superposition of quantum states, we show that such a system demonstrates interesting new effects, such as a ``breathing'' photonic crystal with an oscillating bandgap, and a ``quantum Archimedean screw'' that transports, at an arbitrary controlled velocity, Josephson plasma waves through the transmission line. The key ingredient of these effects is that the optical properties of the Josephson transmission line are controlled by the quantum coherent state of the qubits.