Witnessing topological Weyl semimetal phase in a minimal circuit-QED   lattice
  We present a feasible protocol to mimic topological Weyl semimetal phase in a small one-dimensional circuit-QED lattice. By modulating the photon hopping rates and on-site photon frequencies in parametric spaces, we demonstrate that the momentum space of this one-dimensional lattice model can be artificially mapped to three dimensions accompanied by the emergence of topological Weyl semimetal phase. Furthermore, via a lattice-based cavity input-output process, we show that all the essential topological features of Weyl semimetal phase, including the topological charge associated with each Weyl point and the open Fermi arcs, can be unambiguously detected in a circuit with four dissipative resonators by measuring the reflection spectra. These remarkable features may open a new prospect in using well-controlled small quantum lattices to mimic and study topological phases. 
Feng Mei, Zheng-Yuan Xue, Dan-Wei Zhang, Lin Tian, Chaohong Lee, and   Shi-Liang Zhu
quant-ph cond-mat.mes-hall