Measuring a topological transition in an artificial spin 1/2 system
  We present measurements of a topological property, the Chern number ($C_\mathrm{1}$), of a closed manifold in the space of two-level system Hamiltonians, where the two-level system is formed from a superconducting qubit. We manipulate the parameters of the Hamiltonian of the superconducting qubit along paths in the manifold and extract $C_\mathrm{1}$ from the nonadiabitic response of the qubit. By adjusting the manifold such that a degeneracy in the Hamiltonian passes from inside to outside the manifold, we observe a topological transition $C_\mathrm{1} = 1 \rightarrow 0$. Our measurement of $C_\mathrm{1}$ is quantized to within 2 percent on either side of the transition. 
M. D. Schroer, M. H. Kolodrubetz, W. F. Kindel, M. Sandberg, J. Gao,   M. R. Vissers, D. P. Pappas, Anatoli Polkovnikov and ...
quant-ph cond-mat.mes-hall