Trapped-Ion Quantum Simulator: Experimental Application to Nonlinear   Interferometers
  We show how an experimentally realized set of operations on a single trapped ion is sufficient to simulate a wide class of Hamiltonians of a spin-1/2 particle in an external potential. This system is also able to simulate other physical dynamics. As a demonstration, we simulate the action of an $n$-th order nonlinear optical beamsplitter. Two of these beamsplitters can be used to construct an interferometer sensitive to phase shifts in one of the interferometer beam paths. The sensitivity in determining these phase shifts increases linearly with $n$, and the simulation demonstrates that the use of nonlinear beamsplitters ($n$=2,3) enhances this sensitivity compared to the standard quantum limit imposed by a linear beamsplitter ($n$=1). 
D. Leibfried, B. DeMarco, V. Meyer, M. Rowe, A. Ben-Kish, J. Britton,   W.M. Itano, B. Jelenkovi\'c, C. Langer, T. Rosenband...