Implementation of the Dicke lattice model in hybrid quantum system   arrays
  Generalized Dicke models can be implemented in hybrid quantum systems built from ensembles of nitrogen-vacancy (NV) centers in diamond coupled to superconducting microwave cavities. By engineering cavity assisted Raman transitions between two spin states of the NV defect, a fully tunable model for collective light-matter interactions in the ultra-strong coupling limit can be obtained. Our analysis of the resulting non-equilibrium phases for a single cavity and for coupled cavity arrays shows that different superradiant phase transitions can be observed using existing experimental technologies, even in the presence of large inhomogeneous broadening of the spin ensemble. The phase diagram of the Dicke lattice model displays distinct features induced by dissipation, which can serve as a genuine experimental signature for phase transitions in driven open quantum systems. 
Liujun Zou, David Marcos, Sebastian Diehl, Stefan Putz, J\"org   Schmiedmayer, Johannes Majer, Peter Rabl
quant-ph cond-mat.mes-hall cond-mat.supr-con