Tunable refraction in a two dimensional quantum metamaterial
  In this paper we consider a two-dimensional metamaterial comprising an array of qubits (two level quantum objects). Here we show that a two-dimensional quantum metamaterial may be controlled, e.g. via the application of a magnetic flux, so as to provide controllable refraction of an input signal. Our results are consistent with a material that could be quantum birefringent (beam splitter) or not dependent on the application of this control parameter. We note that quantum metamaterials as proposed here may be fabricated from a variety of current candidate technologies from superconducting qubits to quantum dots. Thus the ideas proposed in this work would be readily testable in existing state of the art laboratories. 
M. J. Everitt, J. H. Samson, S. E. Savelev, T. P. Spiller, R. Wilson,   A. M. Zagoskin
quant-ph cond-mat.mes-hall cond-mat.mtrl-sci