Quantum metamaterials: Eleclectromagnetic waves in Josephson qubit lines

We consider the propagation of a classical electromagnetic wave l through a transmission fine, formed by identical superconducting charge qubits inside a superconducting resonator. Since. the qubits can be in a coherent superposition of quantum itates, we show that such a system demonstrates interesting new effects, such as a breathing photonic crystal with an oscillating bandgap. Similar behaviour is expected from a transmission line formed by flux qubits. 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. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim