Photonic quantum simulation of ground state configurations of Heisenberg   square and checkerboard lattice spin systems
  Photonic quantum simulators are promising candidates for providing insight into other small- to medium-sized quantum systems. The available photonic quantum technology is reaching the state where significant advantages arise for the quantum simulation of interesting questions in Heisenberg spin systems. Here we experimentally simulate such spin systems with single photons and linear optics. The effective Heisenberg-type interactions among individual single photons are realized by quantum interference at the tunable direction coupler followed by the measurement process. The effective interactions are characterized by comparing the entanglement dynamics using pairwise concurrence of a four-photon quantum system. We further show that photonic quantum simulations of generalized Heisenberg interactions on a four-site square lattice and a six-site checkerboard lattice are in reach of current technology. 
Xiao-song Ma, Borivoje Dakic, Sebastian Kropatsche, William Naylor,   Yang-hao Chan, Zhe-xuan Gong, Lu-ming Duan, Anton Zeil...
quant-ph physics.optics