  We study a scheme of quantum simulator for two-dimensional xy-model
Hamiltonian. Previously the quantum simulator for a coupled cavity array spin
model has been explored, but the coupling strength is fixed by the system
parameters. In the present scheme several cavity resonators can be coupled with
each other simultaneously via an ancilla qubit. In the two-dimensional Kagome
lattice of the resonators the hopping of resonator photonic modes gives rise to
the tight-binding Hamiltonian which in turn can be transformed to the quantum
xy-model Hamiltonian. We employ the transmon as an ancilla qubit to achieve in
situ controllable xy-coupling strength.
