EPJ Quantum Technol. (2015) 2: 5
https://doi.org/10.1140/epjqt/s40507-015-0018-0

Research

Phase diagram of a QED-cavity array coupled via a N-type level scheme

¹ NEST, Scuola Normale Superiore and Istituto di Nanoscienze, CNR, Piazza dei Cavalieri, 7, Pisa, 56126, Italy
² Center for Quantum Technologies, National University of Singapore, Singapore, 117543, Singapore

^* e-mail: jiasen.jin@sns.it

Received: 31 July 2014
Accepted: 14 January 2015
Published online: 21 February 2015

Abstract

We study the zero-temperature phase diagram of a one-dimensional array of QED cavities where, besides the single-photon hopping, an additional coupling between neighboring cavities is mediated by an N-type four-level system. By varying the relative strength of the various couplings, the array is shown to exhibit a variety of quantum phases including a polaritonic Mott insulator, a density-wave and a superfluid phase. Our results have been obtained by means of numerical density-matrix renormalization group calculations. The phase diagram was obtained by analyzing the energy gaps for the polaritons, as well as through a study of two-point correlation functions.