Quantum Left-handed metamaterial with superconducting quantum   interference devices
  A scheme of left-handed metamaterial (LHM) composed of superconducting quantum interference devices (SQUIDs) and conducting wires is proposed. The permeability of a probe field can be smoothly tuned over a wide range with another electromagnetic (coupling) field due to quantum interference effect. Similar to electromagnetically induced transparency (EIT) of atomic systems, the absorption of the probe field can be strongly suppressed even in the case of negative permeability. There are two passbands of negative refractive index with low loss, which can be tuned with the coupling field. 
Chunguang Du, Hongyi Chen, Shiqun Li