Measuring a Topological Transition in an Artificial Spin-1/2System

M. D. Schroer, M. H. Kolodrubetz, W. F. Kindel, M. Sandberg, J. Gao, M. R. Vissers, D. P. Pappas, Anatoli Polkovnikov, K. W. Lehnert
2014 Physical Review Letters  
We present measurements of a topological property, the Chern number (C_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_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
more » ... topological transition C_1 = 1 → 0. Our measurement of C_1 is quantized to within 2 percent on either side of the transition.
doi:10.1103/physrevlett.113.050402 pmid:25126902 fatcat:i3dkdzg4vzcozmq3mwxuiqqb6m