Simulating many-body physics using Josephson-junction arrays in circuit-QED architecture*

Josephson-junction arrays (JJAs) in superconducting circuits are prototypical systems which can be designed for various lattice topologies and have the ability to control the chemical potential and associated energy scales for studying the many-body phenomena in both classical and quantum regimes. Here we present microwave studies of JJAs in circuit-QED architecture which have the following advantage over the usual DC transport measurement scheme: the system is only weakly perturbed by microwave excitation, enabling this particular scheme to study properties of the ground state and the excited states at the single-excitation (photon) level. In this talk, we report the observation of lattice ordering of vortices and direct detection of plasma-mode (spin wave) spectra in a 31x3 quasi-1D JJA. We also present some recent results on many-body effects in a 100x100 square-lattice JJA.